Why is Libya lawless?
Libya has been hit by instability since the overthrow of long-serving ruler Col Muammar Gaddafi in October 2011. Numerous militias each govern their own patches of territory, with successive governments struggling to exercise control.Who is in control of Libya?
No-one - that is the problem. There are lots of different armed groups - up to 1,700 - with many different goals. But money and power are the common denominators.
During the uprising, anyone with a gun could command respect and some do not want that to change. Instead, they seem more determined than ever to gain more territory and impose their will.
They are also ideologically divided - some of them are Islamists, others are secessionists and yet others are liberals. Furthermore, the militias are split along regional, ethnic and local lines, making it a combustible mix. Some fear Libya could descend into civil war.Weren't they once allies?
They were united in their hatred for Col Gaddafi - but nothing more. There was no single group in charge of the rebellion. Militias were based in different cities, fighting their own battles.
Several felt they had paid a particularly high price during the conflict and should be rewarded. And after more than four decades of authoritarian rule, they had little understanding of democracy. So, they were unable to forge compromises and build a new state based on the rule of law.
As a result, Libya has had at least five governments since the 2011 revolution. In June 2014, it held its second democratic election since Col Gaddafi's overthrow, but the poll worsened stability as the losers refused to accept defeat.
Libya now has two rival governments, one based in the main city, Tripoli, and the other - the winners of the June election - about 1,000km (620 miles) away in the port city of Tobruk.Has Libya received outside help?
Very little. The US had pledged to help the new government recover weapons - especially anti-aircraft missiles that had been gone missing when Col Gaddafi's government crumbled.
But Libya remains what some security analysts describe as an arms bazaar. It is awash with weapons which have also ended up in the hands of other armed groups in the region. Weapons from Col Gaddafi's looted arsenals are also said to have been smuggled to the Sinai, Gaza and even Syria and Iraq.
The UN belatedly launched a mediation effort in 2014, but it has had little success so far - although partial ceasefires have been announced.
As for regional bodies like the Arab League and African Union (AU), they have shown minimal interest in the Libyan conflict.Why?
The Arab League appeared to be more concerned about the instability in the Middle East and Egypt. As for the the AU, it has little influence in Libya - it opposed the Nato-backed offensive to oust Col Gaddafi, and is viewed with deep suspicion by Libya's authorities.
Yet African countries are most concerned about the conflict, fearing it could worsen instability in countries such as Mali, Niger and Nigeria.
Western powers have now started to take a greater interest in Libya, fearing that the Islamic State (IS), rivalling al-Qaeda as the world's premiere jihadi movement since its emergence last year, is gaining a foothold in the country.
The New York Times has reported that there are IS affiliates in each of Libya's three provinces and in December, US Africa Command head David Rodriguez said the IS had set up training camps in eastern Libya, but he ruled out military action in the foreseeable future.
From bases in Egypt, the United Arab Emirates (UAE) was suspected to have launched air strikes against militias in Tripoli in August in a failed to attempt to help the Tobruk-based government regain control of the city.Have foreigners been threatened?
Yes. There have been a spate of attacks on diplomats since 2012. They include the killing of US Ambassador Christopher Stevens in Benghazi, where the uprising against Col Gaddafi began, and the kidnapping of the Jordanian ambassador Fawaz al-Itan, who was released in exchange for a jihadist jailed in Jordan. There were also attacks on the Italian consulate in Benghazi, as well as the French and the Russian embassies in Tripoli.
And British school teacher David Bolam was taken hostage in Benghazi in May 2014. He was released some five months later apparently after a ransom was paid. In January this year, two Tunisian journalists, Sofiene Chourabi and Nadhir Ktari, were killed after being taken hostage.
The US appears to be carrying out covert operations in Libya to neutralise the threat posed by militants. It responded to Mr Stevens' death by capturing al-Qaeda suspect Anas al-Libya in Tripoli in October 2013 and in June 2014, Ahmed Abu Khattala was seized near Benghazi.
Militias have also seized oil terminals, operated by Western firms. It has led to a huge fall in production, but has not had a major impact on the global oil market.Which are the main militias?
Libya Dawn controls much of western Libya, including Misrata and Tripoli. It is led by fighters from Misrata, the city which took pride in putting up the most fierce resistance against Col Gaddafi's forces. Libya Dawn also includes in its ranks fighters from Zintan, Warshafan and Warfallah.
Its seizure of Tripoli in August 2014 had the backing of Libya's most senior Islamic cleric, Sheikh Sadik Al-Ghariani, who broadcasted messages of support from a location in the UK, urging Libya Dawn to take a "firm hand" in their newly acquired city, according to the London-based Guardian newspaper.
Ansar al-Sharia is in control of the second city Benghazi, the cradle of the 2011 revolution. It is said to be the most dangerous Islamist armed group in Libya, along with its ally, the 17 February Martyrs Brigade.
Ansar al-Sharia was blamed for Mr Stevens' killing, and is said to have forged links with other Islamists groups. Some analysts say it includes men who fought in Syria, though there has been no independent confirmation of this.
The Islamic Youth Shura Council is the most prominent IS-affiliated militia group. It is based in Derna, a small town on Libya's north-eastern coast and some 720 km (450 miles) from Tripoli. In October, its members - said to be led by Saudi preacher Abu al-Baraa el-Azdi - declared that Derna had become the first Libyan town to join the global caliphate that IS has vowed to create.
General Khalifa Haftar also has a powerful militia, the Libyan National Army (LNA). He has cast himself as the main opponent of the Islamist militias and has the backing of the Tobruk-based government and is said to have co-ordinated military activities with Egypt.