Q&A: Lawless Libya
The brief detention of Libyan Prime Minister Ali Zeidan has highlighted the power of the militias set up to topple Muammar Gaddafi in 2011, which still prevent the government from exercising control.
How can a prime minister be kidnapped?
Two years after Col Gaddafi was toppled, the elected government does not really control much of the country - the numerous different armed groups which emerged across Libya to oust him still run many areas.
The government has been unable to disarm them to create a truly national security service.
They are often better armed than the police, or even a particular army unit, so it is not a complete surprise that they were able to overpower the prime minister's bodyguards.
So how does the government work?
The government itself is something of a coalition of groups with varying degrees of links to the militias.
Instead, ministries sometimes employ a group of gunmen to provide security on a particular occasion.
This can be a barely disguised way of paying the militias to not cause trouble.
Is this the first high-profile kidnap?
It is certainly the biggest.
But in September, the daughter of Gaddafi's former spy-chief Abdullah al-Senussi was seized by armed men as she left prison in Tripoli.
It later emerged that a group linked to the interior ministry had taken her for own protection and she was released unharmed after a few days.
But it is obviously a precursor of what was to come.
Is the lawlessness affecting the whole country?
Some groups based in the east, around Benghazi, have blockaded the ports and oil terminals over the past month, severely restricting exports of Libya's major foreign currency earner, which mostly comes from the region.
In September, this was estimated to be costing the country some $130m (£80m) a day.
What do the militias want?
There are lots of different armed groups - up to 1,700 - with many different goals. But money and power is a common denominator.
During the uprising, anyone with a gun could command respect and some do not want that to change.
While some groups provide social services in the areas they control, others are making money by trafficking drugs, migrants and oil.
Like any country, Libya has regional rivalries and most of the armed groups have strong local identities.
The uprising against Gaddafi began in Benghazi, where many felt was marginalised by him. Some local leaders feel nothing has really changed and want more power, or even independence for the region that was historically known as Cyrenaica.
Groups based around Misrata, further west, feel that they suffered the most during the battle against Gaddafi and they want some recognition for this. They, too, are unwilling to surrender their weapons to people from Tripoli.
In Zintan, south-east of the capital, the armed group that captured Gaddafi's son Saif al-Islam in September refused to hand him over to the central government, saying it wants to put him on trial locally.
Some of the militias have an Islamist agenda and have links to al-Qaeda.
These are likely to have been particularly incensed by the US raid to capture terror suspect Anas al-Liby in Tripoli.