Although Bashar al-Assad inherited Syria's presidency on his father's death in 2000, analysts say he does not have Hafez al-Assad's absolute grip on power. He is surrounded by military and intelligence figures, most of whom are either related to the president or are members of his minority Alawite community.
Maher al-Assad, Republican Guard chief
The president's youngest brother is said to be Syria's second most powerful man. He heads the Republican Guard, the elite force whose six brigades protect the regime from domestic threats, and commands the fourth armoured division, considered one of the army's best-equipped and highly-trained.
Born in 1967, Maher studied at the University of Damascus. He later followed his older brother Basil into the military. Some thought he might be named Hafez's successor after Basil's death in 1994, but he was too young and Bashar was chosen.
Before his promotion to general, Maher commanded a Republican Guard brigade. This provided him with valuable military experience and allowed him to establish personal ties with many officers.
In 2000, shortly after Bashar became president, Maher became a member of Baath Party's second highest body, the Central Committee.
He has a reputation for being excessively violent and emotionally unstable, and allegedly shot and wounded his brother-in-law, Asef Shawkat.
In 2000, Maher is reported to have helped persuade Bashar to put an end to the political openness seen during the first few months of his rule - the short-lived "Damascus Spring". Years of suppression followed.
Three years later, Israeli media said Maher had attended a series of informal meetings in Jordan with the director of Israel's foreign minister and two Israeli-Arab businessmen to discuss resuming peace talks.
In 2005, Maher and Shawkat were both mentioned in a preliminary report by UN investigators as one of the people who might have planned the assassination of the former Lebanese Prime Minister, Rafik Hariri.
When mass pro-democracy protests began in the southern city of Deraa in March 2011, Maher's fourth armoured division - a successor to Rifaat al-Assad's Defence Brigades which is deployed on Syrian territory bordering the Israeli-occupied Golan Heights, and controls the capital's approaches - was sent in to crush them. Human rights activists say dozens of people have since been killed.
At one protest in Deraa, many shouted slogans denouncing Maher, including: "Maher you coward. Send your troops to liberate the Golan."
By late April, witnesses said the fourth division's tanks had cut off Deraa and were shelling residential areas, while troops were storming homes and rounding up people believed to have been taking part in the protests.
The US subsequently announced sanctions against Maher, saying the fourth division had "played a leading role in the Syrian regime's actions in Deraa". The EU also imposed sanctions on Maher, describing him as the "principal overseer of violence against demonstrators".
In May 2011, a video emerged purportedly showing Maher, dressed in a leather jacket and surrounded by police officers, firing a rifle at unarmed protesters in the Damascus suburb of Barzeh.
The next month, Turkish Prime Minister Recep Tayyip Erdogan told reporters: "I say this clearly and openly, from a humanitarian point of view, [Maher] is not behaving in a humane manner. And he is chasing after savagery."
Rumours persist that Maher might challenge his brother's rule - much like his uncle Rifaat attempted to seize power from Hafez in 1983 - but there is no evidence that he has sufficient power to challenge his rule.
A first cousin of Bashar al-Assad, Mr Makhlouf is arguably the most powerful economic figure in Syria. He has been the subject of persistent accusations of corruption and cronyism, and analysts say no foreign companies can do business in Syria without his consent.
Born in 1969, Mr Makhlouf took over the businesses built up by his father, Mohammed, the brother of Hafez al-Assad's wife, Anisa Makhlouf. After Bashar became president in 2000, Mr Makhlouf's financial empire expanded.
In 2001, he and the Egyptian telecommunications company, Orascom, were awarded one of Syria's two mobile phone operator licences. After a court dispute over control of Syriatel, Orascom was forced to sell its 25% stake.
When Riad Seif, an opposition MP, criticised the "irregularities" in the awarding of the phone licences, he was arrested and imprisoned.
In addition to Syriatel, Mr Makhlouf is believed to control two banks, free trade zones, duty free shops, a construction company, an airline, two TV channels, and imports luxury cars and tobacco. He also owns shares in and is vice-chairman of Cham Holding, considered Syria's largest private company, and has stakes in several oil and gas companies.
In 2008, the US treasury banned US firms and individuals from doing business with Mr Makhlouf, and froze his US-based assets. It accused him of "corrupt behaviour", "disadvantaging innocent Syrian businessmen and entrenching a regime that pursues oppressive and destabilising politics".
"Makhlouf has manipulated the Syrian judicial system and used Syrian intelligence officials to intimidate his business rivals. He employed these techniques when trying to acquire exclusive licenses to represent foreign companies in Syria and to obtain contract awards," a statement said.
"Despite President Assad's highly publicised anti-corruption campaigns, Makhlouf remains one of the primary centres of corruption in Syria."
The US imposed sanctions on Mr Makhlouf's younger brother, Hafez- a senior official in the General Security Directorate - in 2007 for his connection with efforts to reassert Syrian control over Lebanon.
Former Vice-President Abdul Halim Khaddam said in 2009 that Bashar's rule had been marked by "transforming corruption into an institution" headed by Mr Makhlouf. He said corruption, suppression of dissent, and economic hardship were pushing Syrians over the edge.
Two years later, anti-government protesters in Deraa initially directed their wrath at Mr Makhlouf, some chanting: "We'll say it clearly, Rami Makhlouf is robbing us". A branch of Syriatel in Deraa was set on fire.
Opposition websites later accused Mr Makhlouf of financing pro-government demonstrations both across Syria and abroad, by providing flags, meals and money for those participating.
In May 2011, the EU imposed sanctions against Mr Makhlouf, saying he was an "associate of Maher al-Assad" who "bankrolls the regime allowing violence against demonstrators".
The tycoon insists his businesses are legitimate and provide professional employment for thousands of Syrians.
Following the US sanctions announcement in 2007, he told the BBC that the designation was tantamount to "a medal we hang on our chest", and was part of a "political ploy aimed at undermining important individuals".
President Assad is reported to have been angered by an interview Mr Makhlouf gave to the New York Times in May 2011, in which he said the government would fight "until the end" and that it would "not suffer alone". He also said that regime change in Syria could push the Middle East into turmoil and even war. Syria's ambassador to the US responded by saying Mr Makhlouf was a "private citizen" who did not "speak on behalf of the Syrian authorities".
The next month Mr Makhlouf announced that he was quitting business and moving into charity work. He told a televised news conference that he would offer shares of Syriatel to the poor and that profits would go, in part, to the families of those killed in the uprising. Profits from other businesses would go to charitable and humanitarian organisations, Mr Makhlouf added, promising not to enter any new business venture that would bring him personal gain.
Opposition figures doubted the sincerity, though it did seem a member of the president's inner circle was being forced to publicly step aside.
In August 2011, the US imposed sanctions on Syriatel, saying the Syrian government had directed the company to "sever network connectivity in areas where attacks were planned" and that it had recorded mobile-phone conversations for the security services.
Ali Mamluk, director of the National Security Bureau (NSB)
Born in 1946, Lt Gen Mamluk is the director of the Baath Party Regional Command's National Security Bureau (NSB), which in theory co-ordinates the work of Syria's intelligence agencies and formulates recommendations for the president. In practice, however, the agencies operate with a high degree of autonomy, answerable mainly to the president.
Between 2005 and 2012, he was head of the General Security Directorate (State Security), where he was involved in some of the most sensitive issues concerning Syria. Before that he was deputy head of the feared Air Force Intelligence.
A leaked US classified diplomatic cable discussing whether to impose financial sanctions on Gen Mamluk in 2007 said he was well known for his "objectionable activities regarding Lebanon, and his suppressing Syrian civil society and the internal opposition". The embassy in Damascus said sanctions against Gen Mamluk would "resonate well" in the country.
Despite this, Gen Mamluk discussed efforts to increase co-operation between Washington and Damascus on terrorism issues at a surprise meeting with US diplomats in 2010, according to a leaked US classified cable. He said the GSD had been more successful at fighting terrorism in the region because "we are practical and not theoretical".
In April 2011, the US government imposed sanctions on Gen Mamluk, saying he had been responsible for human rights abuses, including through the use of violence against civilians.
His agency had repressed internal dissent, monitored individual citizens, and had been "involved in the Syrian regime's actions in Deraa, where protesters were killed by Syrian security services", it alleged.
The next month, the EU also imposed sanctions on Gen Mamluk, saying he had been involved in efforts to crush anti-government protesters.
A Sunni from Damascus, he is said to be on good terms with all of Syria's intelligence agencies - Jamil Hassan, the head of Air Force Intelligence, and Mohammed Dib Zaitoun, the General Security Directorate chief, were once his assistants.
The US also said in April that Gen Mamluk had overseen a communications programme directed at opposition group and had received both technological and analytical support from Iran's ministry of intelligence and security (MOIS). Mamluk had "worked with the MOIS to provide both technology and training to Syria, to include internet monitoring technology" and "requested MOIS training and assistance on social media monitoring and other cyber tools for the GSD", it added.
Rami Abdul Rahman, the head of the UK-based Syrian Observatory for Human Rights, said Gen Mamluk had also met several opposition figures inside Syria to "incite them to renounce violence and back the reforms of the Assad regime".
President Assad asked Gen Mamluk to lead the National Security Bureau after its director, Gen Hisham Ikhtiar, died after a bomb attack on its headquarters on 18 July 2012, Syrian officials and Lebanese media reported. The blast also killed Mr Assad's brother-in-law, Deputy Defence Minister Gen Assef Shawkat, Defence Minister Gen Daoud Rajiha, and former Defence Minister Hassan Turkomani, who was in charge of the security forces' crisis management office.
Abdul Fatah Qudsiya, deputy director of the National Security Bureau
Gen Qudsiya became deputy director of the National Security Bureau (NSB) in July 2012. He had previously been head of Military Intelligence, the paramount security agency in Syria.
Before replacing the president's late brother-in-law, Assef Shawkat, as military intelligence chief sometime between 2005 and 2009, he was head of Air Force Intelligence.
Earlier in his career, Gen Qudsiya - an Alawite born in 1953 - served as head of the Republican Guard's security office, and as personal secretary to the president.
Gen Qudsiya was asked in 2008 to lead the security committee investigating the assassination of Hezbollah military commander Imad Mughniyeh in Damascus. The committee notably did not include Gen Shawkat, who was criticised for failing to prevent the killing.
In May 2011, Gen Qudsiya was included in a list of Syrian officials subjected to EU sanctions for their roles in violence against protesters. Military Intelligence is said to have played a prominent role in the crackdown, firing on crowds of protesters and killing a large number of civilians.
The US also imposed sanctions on Gen Qudsiya later that month, accusing his agency of using force against and arresting demonstrators participating in the unrest.
Gen Qusiya was appointed Gen Ali Mamluk's deputy at the National Security Bureau following the bomb attack on its headquarters in Damascus on 18 July, Syrian officials and Lebanese media reported.
Rafiq Shahada, head of Military Intelligence
Maj Gen Rafiq Shahada is believed to be the head of Military Intelligence, the paramount security agency in Syria, which has a reputation for ruthless efficiency and whose leaders have wielded considerable influence over presidents.
As well as strategic and tactical intelligence, the agency has a critical role in ensuring the leadership's physical security and the loyalty of the army.
In August 2011, the EU imposed sanctions on Gen Shahada, describing him as head of Military Intelligence's Branch 293, which is responsible for internal affairs, in Damascus. He was accused of being "directly involved in repression and violence against the civilian population" in the capital. The EU also said Gen Shahada was also serving as adviser to President Assad for strategic questions and military intelligence.
Gen Shahada was promoted to chief of Military Intelligence in July 2012 after his predecessor, Abdul Fatah Qudsiya, became deputy head of the National Security Bureau, according to Syrian officials and Lebanese media reports. One unconfirmed report said Gen Shahada had until then been head of Military Intelligence in Homs.
Jamil Hassan, head of Air Force Intelligence
Maj Gen Hassan replaced Abdul Fatah Qudsiya as head of Air Force Intelligence in 2009.
Though smaller than Military Intelligence, AFI is seen by some as the elite agency of Syria's intelligence empire. The agency owes its power to Hafez al-Assad, who was air force chief before coming to power in a coup. It plays a leading role in operations against Islamist opposition groups, as well as covert actions abroad, and has a reputation for brutality.
Gen Hassan, an Alawite, previously served as a security official in the eastern governorate of Deir al-Zour.
In late April 2011, personnel from Air Force Intelligence fired tear gas and live ammunition to disperse crowds of demonstrators who took to the streets in Damascus and other cities after noon prayers, killing at least 43 people, according to the US. In one incident in Nawa, PSD agents reportedly opened fire on a crowd of protesters waiving olive branches.
The next month, the EU said Gen Hassan was "involved in the repression against the civilian population" during the recent anti-government unrest, and imposed a travel ban and asset freeze on him.
Mohammed Dib Zaitoun, head of the General Security Directorate
Maj Gen Zaitoun, a Sunni born in 1951, is reportedly the new head of the General Security Directorate (GSD), which is the most powerful civilian intelligence agency and plays an important role in quelling internal dissent.
Tasked primarily with safeguarding against and preventing domestic subversion and organised crime, the GSD is organised into three branches - internal security, external security and Palestinian affairs. It controls the civilian police and the border guards, and has primary responsibility for surveillance of the Baath Party, the state bureaucracy and the general population.
Gen Zaitoun was previously head of the Political Security Directorate (PSD) between 2009 and 2012, and before then deputy head of the GSD.
In 2008, he was asked - along with other members of the president's inner circle - to investigate the assassination of Hezbollah's Imad Mughniyeh in Damascus.
In May 2011, the EU accused Gen Zaitoun of involvement in violence against demonstrators, and announced a travel ban and asset freeze. The US also imposed sanctions on him later that month, accusing him of human rights abuses.
Gen Zaitoun became head of the GSD in July 2012 following the bomb attack on the National Security Bureau in Damascus which killed four senior security chiefs, Syrian officials and Lebanese media reported.
Rustum Ghazali, head of the Political Security Directorate
Gen Ghazali is the head of the Political Security Directorate, a civilian agency that is responsible for monitoring organised political activity, including surveillance of registered parties and political publications. It also has a regional surveillance brief, covering Arab, Palestinian and Israeli affairs.
Born in 1953, he is a former chief of Syrian Military Intelligence in Lebanon, and was in the post when Rafik Hariri was assassinated.
Gen Ghazali assumed command in 2002, and was the "implementing agent of Syrian policies in Lebanon" until the Syrian withdrawal in 2005, according to the US treasury department. It accused Gen Ghazali of manipulating Lebanese politics to ensure officials and public policy remained committed to Syria's goals and interests. He reportedly used his influence to ensure former President Emile Lahoud's term of office was renewed, while Lebanon's military chiefs allegedly reported to him.
After the withdrawal from Lebanon little was heard of him. However, at the beginning of the protests in the city of Deraa, Gen Ghazali was sent by Bashar al-Assad to assure locals of the president's good intentions. He reportedly told them: "We have released the children" - a reference to several teenagers who were arrested for writing anti-regime graffiti inspired by the events in Egypt and Tunisia.
In May 2011, the EU said Gen Ghazali was head of Military Intelligence in Damascus Countryside (Rif Dimashq) governorate, which borders Deraa governorate, and was involved in "violence against the civilian population". The US imposed individual sanctions on Gen Ghazali the next month, saying he was a high-ranking member of Military Intelligence.
In July 2012, Gen Ghazali was appointed head of the PSD following the bomb attack on the National Security Bureau in Damascus, Syrian officials and Lebanese media reported. His appointment firmly quashed rumours that he had defected the previous week.
Hafez Makhlouf, head of the General Security Directorate in Damascus
Col Makhlouf is head of the Damascus branch of the General Security Directorate, the overarching civilian intelligence service in Syria.
Born in 1971, he is a maternal cousin and childhood friend of President Bashar al-Assad, and the brother of Rami Makhlouf.
Col Makhlouf is perhaps best known for being one of the two survivors of the high-speed car crash in 1994 that killed the president's elder brother, Basil, who was being groomed to succeed their father, Hafez.
In 2007, the US treasury department designated him an individual "furthering the Syrian regime's efforts to undermine Lebanese democracy" and froze his assets. It alleged that he had "supported the reassertion of Syrian control or otherwise contributed to Syrian interference in Lebanon". Syrian troops withdrew from Lebanon in April 2005 after a 29-year military presence.
In May 2011, the EU imposed sanctions on Col Makhlouf, saying he was "close to Maher al-Assad" had been "involved in violence against demonstrators" as head of the GSD's Damascus branch.
The US treasury department announced new sanctions against him later that month, saying he had been "given a leading role in responding to protests in Syria, and was heavily involved in the Syrian regime's actions in Deraa, where protesters were killed".
Opposition activists have said Col Makhlouf enjoys greater influence over the president than the head of the GSD, Ali Mamluk.
Mohammed Nasif Kheirbek, deputy vice-president for security affairs
Gen Kheirbek is a member of the Alawite Kalabiya tribe, to which Bashar al-Assad belongs. Their families are also connected by marriage - a relative is married to one of Rifaat al-Assad's daughters.
The general, who was born in 1937 and is reported to have medical problems, has long served the Syrian regime and remains an influential adviser to the president. He was a very close adviser to the late Hafez al-Assad before being appointed deputy director of the General Security Directorate (GSD) in 1999.
He served in the position until 2006, when he was named deputy vice-president for security affairs. The next year, the US froze his assets for "contributing to the government of Syria's problematic behaviour", which it said included support of international terrorism, the pursuit of weapons of mass destruction, and the undermining of efforts in Iraq.
A leaked US diplomatic cable described Gen Kheirbek as Syria's "point-man for its relationship with Iran". It said designating him could "heighten Syrian and regional concerns about the [government's] willingness to accommodate an expansionary Iranian agenda".
In May 2011, the EU imposed sanctions on Gen Kheirbek, saying he had been "involved in violence against the civilian population".
The next month, the general reportedly travelled to Tehran to meet Gen Qasem Soleimani, commander of the Quds Force, the elite overseas operations arm of Iran's Islamic Revolution Guards Corps (IRGC). They are said to have discussed opening a supply route that would enable Iran to transfer military hardware directly to Syria via a new military compound at Latakia airport.
Dhu al-Himma Shalish, head of Presidential Security
Gen Shalish is Bashar's first cousin and head of Presidential Security, an elite force. In June 2011, the EU imposed sanctions of him, saying he had been "involved in violence against demonstrators".
He once owned SES International, which the US government alleged in 2005 was a "vehicle to put military goods into the hands" of former Iraqi leader Saddam Hussein and his regime.
He and his brother, Assef, who managed SES, acted as a "false end user" for Iraq, helping to procure defence-related goods for the Iraqi military before the US-led invasion, it added. SES allegedly provided exporters with end-user certificates indicating Syria was the final destination, and then shipped them illegally to Iraq. He was said to have provided close personal assistance to Saddam's oldest son, Uday.
Gen Shalish's influence within the president's inner circle is believed to have increased since the beginning of the uprising. Joshua Landis of the University of Oklahoma told the New York Times in July 2012 that he was now a key financier and organiser of feared pro-Assad militiamen known as "shabiha", who activists say have been used by the government to intensify the crackdown on protesters and commit atrocities on its behalf.
Gen Shalish and his immediate family were "looked at as lowlife no-goodniks a year ago, but today they have been catapulted into the ranks of the inner circle because they are willing to do the dirty work for the regime," Mr Landis said. "There are only so many family members."
Zuhair Hamad, deputy head of the General Security Directorate
Maj Gen Hamad is deputy to Mohammed Dib Zaitoun, the head of the powerful General Security Directorate.
He previously led its Special Intelligence Unit, he was responsible for monitoring newspapers, television channels and websites covering Syria, and writing daily reports for high-ranking officials. Opposition sources said he often summoned journalists for "clarification" on their stories, and accused him of often resorting to blackmailing them to limit criticism of the regime.
Human rights activists say Gen Hamad played a major role in the campaign of arrests against opposition and independent figures which intensified in the months leading up to the recent anti-government unrest.
In November 2011, the EU accused Gen Hamad of responsibility "for the use of violence across Syria and for intimidation and torture of protesters" and imposed sanctions on him.