Aydabiya under surprse attack from Libyan government forces

The rebels said they had managed to repulse the attack after several hours of fighting.

Doctors said eight rebels were killed in the violence.

Meanwhile, in the western city of Misrata, Nato forces have intensified their air strikes and destroyed 15 tanks after an upsurge of violence.

Rebel leaders have been critical of Nato's attempts to enforce a UN-mandated no-fly zone, particularly since an air strike hit a rebel convoy earlier this week.

But rebel commanders now say they are heartened by the intensification of strikes on pro-Gaddafi forces on Friday and Saturday

Nato announced that its jets had destroyed government ammunition stockpiles east of the capital Tripoli, tanks around Misrata and also military vehicles near Brega.

The Nato operation has diminished the government's firepower, but pro-Gaddafi commanders have switched tactics.

On Saturday, as rebel fighters headed west from Ajdabiya towards Brega, government troops in pick-up trucks took desert roads and entered Ajdabiya.

The BBC reports that a rebel fighter, Salah Ali, said that pro-Gaddafi soldiers had spread out in the city, and had begun fighting with weapons including heavy machine guns and grenade launchers.

The fighting raged for much of Saturday, and pockets of violence were still being reported after rebel commanders said they had beaten off the attack.

A team of African leaders headed by South African President Jacob Zuma is due in Benghazi later to hold talks with the rebels.

And UN Secretary General Ban Ki-moon will host a meeting of international and regional organisations in Cairo on Thursday aimed at co-ordinating the response to the crisis in Libya.