Fierce fighting closed Tripoli international airport on Saturday night as rival militias battled for control of the facility in the latest upsurge of violence in Libya's volatile capital.

Hours after Libya's president, Mustafa Abdul Jalil, made a plea for all sides to work for reconciliation, unidentified militia attacked the airport garrison.

Television footage showed exchanges of fire at the perimeter of the airport, which is held by militia from the town of Zintan, 90 miles south of the capital, under the control of defence minister Osama Jweli.

A camera crew from al-Jazeera reported they were assaulted by gunmen close to the scene of the fighting. Hours later Tripoli airport was shut and Libya closed airspace over the capital amid fears that three pickup trucks mounting anti-aircraft guns, stolen by militia fighters, could be used to target incoming airliners.

In a separate incident, the commander-in-chief of the Libyan national army, Major General Khalifa Belgasim Haftar, was ambushed by gunmen who set up a checkpoint in the capital and attacked his convoy. Haftar's spokesman said the general's jeep managed to escape and two militiamen were later arrested.

The fighting underlines the instability of the Libyan capital, despite the efforts of the city authorities to clamp down on rogue militias earlier last week.

Since Tuesday the capital has been dotted with checkpoints with cars searched and streets blocked off in an effort to check the daily gun battles raging on the streets.

The withdrawal of out-of-town militias from Zintan and Misrata last week, supposedly to allow Tripoli to police itself, appears to have backfired with local turf wars taking place amid a security vacuum. Last week saw pro-Gaddafi gunmen attack the central hospital and the attorney general reportedly attacked in his car.

One security source blamed the violence on the introduction of numerous private militias, recruited by local businessmen from among unemployed young men in a city littered with weapons, and deployed to protect shops and businesses.

Jalil made his plea for calm at a National Reconciliation Conference held in Tripoli, his call echoed by one of the world's most influential Islamic clerics, Yusuf al-Qaradawi.

Al-Qaradawi, an Egyptian trustee of the Oxford University Centre for Islamic Studies, urged former rebels and forces loyal to the late dictator, Muammar Gaddafi, to come together: "We want people reconciling, we don't want people full of hatred. Let somebody lead you."