Who are Nigeria's Boko Haram Islamists?
Nigeria's militant Islamist group Boko Haram - which has caused havoc in Africa's most populous country through a wave of bombings, assassinations and now abductions - is fighting to overthrow the government and create an Islamic state.
Its followers are said to be influenced by the Koranic phrase which says: "Anyone who is not governed by what Allah has revealed is among the transgressors".
Boko Haram promotes a version of Islam which makes it "haram", or forbidden, for Muslims to take part in any political or social activity associated with Western society.
This includes voting in elections, wearing shirts and trousers or receiving a secular education.
Boko Haram regards the Nigerian state as being run by non-believers, even when the country had a Muslim president.
The group's official name is Jama'atu Ahlis Sunna Lidda'awati wal-Jihad, which in Arabic means "People Committed to the Propagation of the Prophet's Teachings and Jihad".Recruiting ground
But residents in the north-eastern city of Maiduguri, where the group had its headquarters, dubbed it Boko Haram.
Loosely translated from the region's Hausa language, this means "Western education is forbidden".
Boko originally meant fake but came to signify Western education, while haram means forbidden.Boko Haram at a glance
- Founded in 2002
- Official Arabic name, Jama'atu Ahlis Sunna Lidda'awati wal-Jihad, means "People Committed to the Propagation of the Prophet's Teachings and Jihad"
- Initially focused on opposing Western education - gaining the nickname Boko Haram, which means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Founding leader Mohammed Yusuf (pictured above) killed in 2009 same year in police custody, succeeded by Abubakar Shekau
- Thousands killed, mostly in north-eastern Nigeria - also attacked police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013
Since the Sokoto caliphate, which ruled parts of what is now northern Nigeria, Niger and southern Cameroon, fell under British control in 1903, there has been resistance among some of the area's Muslims to Western education.
They still refuse to send their children to government-run "Western schools", a problem compounded by the ruling elite which does not see education as a priority.
Against this background, the charismatic Muslim cleric, Mohammed Yusuf, formed Boko Haram in Maiduguri in 2002. He set up a religious complex, which included a mosque and an Islamic school.
Many poor Muslim families from across Nigeria, as well as neighbouring countries, enrolled their children at the school.
But Boko Haram was not only interested in education. Its political goal was to create an Islamic state, and the school became a recruiting ground for jihadis.
In 2009, Boko Haram carried out a spate of attacks on police stations and other government buildings in Maiduguri.
This led to shoot-outs on Maiduguri's streets. Hundreds of Boko Haram supporters were killed and thousands of residents fled the city.Facial marks
Nigeria's security forces eventually seized the group's headquarters, capturing its fighters and killing Mr Yusuf.
His body was shown on state television and the security forces declared Boko Haram finished.
But its fighters regrouped under a new leader, Abubakar Shekau, and have stepped up their insurgency.
In 2010, the US designated it a terrorist organisation, amid fears that it had developed links with other militant groups, such as al-Qaeda in the Islamic Maghreb, to wage a global jihad.
The deployment of troops has driven many of the militants out of Maiduguri, their main urban base”
Boko Haram's trademark was originally the use of gunmen on motorbikes, killing police, politicians and anyone who criticises it, including clerics from other Muslim traditions and Christian preachers.
The group has also staged more audacious attacks in northern and central Nigeria, including bombing churches, bus ranks, bars, military barracks and even the police and UN headquarters in the capital, Abuja.
Amid growing concern about the escalating violence, President Goodluck Jonathan declared a state of emergency in May 2013 in the three northern states where Boko Haram is the strongest - Borno, Yobe and Adamawa.
It draws its fighters mainly from the Kanuri ethnic group, which is the largest in the three states. Most Kanuris have distinctive facial scars and when added to their heavy Hausa accents, they are easily identifiable to others Nigerians.
As a result, the militants operate mainly in the north-east, where the terrain is also familiar to them.Chronic poverty
Northern Nigeria has a history of spawning militant Islamist groups”
The deployment of troops has driven many of them out of Maiduguri, their main urban base and they have now retreated to the vast Sambisa forest, along the border with Cameroon.
From there, the group's fighters have launched mass attacks on villages, looting, killing and burning properties in what appeared to be a warning to rural people not to collaborate with the security forces, as residents of Maiduguri had done.
Boko Haram has also stepped up its campaign against Western education, which it believes corrupts the moral values of Muslims, especially girls, by attacking two boarding schools - in Yobe in March and in Chibok in April.
It abducted more than 200 schoolgirls during the Chibok raid, saying it would treat them as slaves and marry them off - a reference to an ancient Islamic belief that women captured in conflict are part of the "war booty".
It made a similar threat in May 2013, when it released a video, saying it had taken women and children - including teenage girls - hostage in response to the arrest of its members' wives and children. There was later a prison swap, with both sides releasing the women and children.
At the same time, Boko Haram has continued with its urban bombing campaign, targeting the capital on 14 April, when at least 70 people were killed in an explosion near a car park and on 2 May when 19 people died.
This shows that not only does Boko Haram have a fighting force of thousands of men, but also cells that specialise in bombings.
Analysts say northern Nigeria has a history of spawning militant Islamist groups, but Boko Haram has outlived them and has proved to be far more lethal, with a global jihadi agenda.
The threat will disappear only if Nigeria's government manages to reduce the region's chronic poverty and builds an education system which gains the support of local Muslims, the analysts say.
Despite its vast resources, Nigeria ranks among the most unequal countries in the world, according to the UN. The poverty in the north is in stark contrast to the more developed southern states. While in the oil-rich south-east, the residents of Delta and Akwa Ibom complain that all the wealth they generate flows up the pipeline to Abuja and Lagos.
Nigeria's 160 million people are divided between numerous ethno-linguistic groups and also along religious lines. Broadly, the Hausa-Fulani people based in the north are mostly Muslims. The Yorubas of the south-west are divided between Muslims and Christians, while the Igbos of the south-east and neighbouring groups are mostly Christian or animist. The Middle Belt is home to hundreds of groups with different beliefs, and around Jos there are frequent clashes between Hausa-speaking Muslims and Christian members of the Berom community.
Southern residents tend to have better access to healthcare, as reflected by the greater uptake of vaccines for polio, tuberculosis, tetanus and diphtheria. Some northern groups have in the past boycotted immunisation programmes, saying they are a Western plot to make Muslim women infertile. This led to a recurrence of polio, but the vaccinations have now resumed.
Female literacy is seen as the key to raising living standards for the next generation. For example, a newborn child is far likelier to survive if its mother is well-educated. In Nigeria we see a stark contrast between the mainly Muslim north and the Christian and animist south. In some northern states less than 5% of women can read and write, whereas in some Igbo areas more than 90% are literate.
Nigeria is Africa's biggest oil producer and among the biggest in the world but most of its people subsist on less than $2 a day. The oil is produced in the south-east and some militant groups there want to keep a greater share of the wealth which comes from under their feet. Attacks by militants on oil installations led to a sharp fall in Nigeria's output during the last decade. But in 2010, a government amnesty led thousands of fighters to lay down their weapons.