Brega (Libya): Under heavy shelling from advancing government forces, Libyan rebels were forced to abandon another key town on Sunday. Dozens of rebels were seen leaving the coastal town of Brega and heading for Ajdabiya, 80 kilometres away on the road to the main rebel cities of Benghazi and Tobruk.

Rebel sources said forces loyal to strongman Muammar Gaddafi were approaching from the west, and Libyan state television, quoting an unspecified military source, later declared Brega "purged of the armed gangs."

In Benghazi, 240 kilometres east of Brega, all mobile telephone services were suddenly cut for an unknown reason. It was not immediately clear if other rebel-held areas were also affected.

Meanwhile, international backing grew slowly for a no-fly zone over the country.

Rebel morale had been boosted by an Arab League decision on Saturday to support a no-fly zone over Libya and to make contact with the insurgents' provisional national council in Benghazi.

But apart from defectors from Gaddafi’s army, the rebels have no military experience, few heavy weapons and are virtually powerless against air attack.

Declaring Gaddafi had lost all legitimacy, Arab Foreign Ministers urged the UN Security Council "to assume its responsibilities in the face of the deteriorating situation in Libya and take the necessary measures to impose an air exclusion zone for Libyan warplanes."

The United States welcomed the decision, which "strengthens the international pressure on Gaddafi and support for the Libyan people," White House spokesman Jay Carney said in a statement.

"The international community is unified in sending a clear message that the violence in Libya must stop, and that the Gaddafi regime must be held accountable.

"The United States will continue to advance our efforts to pressure Gaddafi, to support the Libyan opposition, and to prepare for all contingencies, in close coordination with our international partners," Carney added.

But he stopped short of giving full support for the no-fly zone which is being pushed for by Britain and France especially, reflecting divisions in the administration of President Barack Obama.