Tripoli's militias are under the spotlight as never before as officials investigate Thursday's kidnapping of the prime minister, Ali Zeidan.

Revolutionary Operations Room of Libya

The spotlight for the kidnapping has fallen the gunmen of the Revolutionary Operations Room, which is the headquarters of a group of former rebel militias called the Libya Shield who were drafted in from other parts of the country during the summer by the congress leader, Nuri Abu Sahmain. Early reports said this headquarters had ordered the capture of Zeidan, which they called an arrest.

Most Shield units drive beaten-up pickup trucks with mounted machine guns that date from the 2011 revolution, still sporting the black paintwork applied to make them distinguishable to Nato bombers. Some units are better equipped: one Misrata group appeared in Tripoli in the summer in a gleaming red and chrome jeep, its armament consisting of four polished silver anti-tank missiles fixed to the rollbars.

Supreme Security Committee

The Supreme Security Committee (SSC), which operates in bright red pickup trucks, is an independent gendarmerie based at Mitiga, a military airbase in the heart of the city. There was controversy when the justice minister, Salah Marghani, said he had been refused access to the prison at Mitiga, despite the SSC being on the government payroll.

The commander of the Tripoli-based SSC's elite Deterrence Force, Hashim Bishar, insists the independence of his militia is the only guarantee of security in a turbulent city. His units have won admirers for tackling Tripoli's drug gangs in a series of gun battles.

Zintanis

The Zintan militias are battle-hardened former rebels from the Nafusa mountains 90 miles south-west of Tripoli who liberated the capital and have stayed on. Their base at Tripoli airport, close to the US embassy, has been the source of tension with rival militias keen for the airport security contract, but many passengers have noted that since the Zintanis arrived the airport has been violence-free.

This summer a group of Zintani militiamen attacked the headquarters of the defence ministry's petroleum guard, after the Zintan contract for guarding oil fields was given to another group. Zintani and SSC units clashed in the western suburb of Salah-Eldeen in August.

Government units

The government is pushing to replace the militias with its own forces. Black and white diplomatic protection jeeps stake out embassies, and regular police have red and white jeeps still sporting logos from their donors in Doha – though they scattered from the Corinthian hotel when the prime minister was seized. Interior ministry officials in fully armoured jeeps with black and grey stripes have won plaudits for confiscating tinted windows from cars. Piles of these windows, a favourite with gangsters, now lie discarded at traffic intersections.