Battles erupt in Az-Zawiyah and Ras Lanuf, as imposition of no-fly zone still in talks

Some of the most severe fighting is taking place in the strategic oil city of Az-Zawiyah, 50km west of the capital Tripoli.

"The revolutionaries control the centre of Zawiyah and Gadhafi's forces are surrounding it. It's 50-50," a resident who fled the city said.

"There was no one in the streets, the town is completely deserted, and there are snipers on the roofs," he said, adding that he did not know which side they were on.

Forces loyal to Gaddafi say they have wrested the city from the hands of rebels, but the claim has been denied by those against the Libyan leader.

News agency Al Jazeera said it is difficult to confirm claims and counter-claims since journalists are unable to reach the city.

But residents said the city had been under sustained attack from pro-Gaddafi forces, aided by tanks and war planes.

Fighting is also being reported in the eastern port city of Ras Lanuf, where an oil installation has gone up in flames.

A journalist for Al Jazeera said an eruption of mortar and rocket fire blanketed the sky with dark smoke, turning day to night.

"Pro-Gaddafi forces unleash a savage counter-offensive against the town of Ras Lanuf," Jacky Rowland said. "Rebel fighters sitting on the ground are vulnerable, and they know it."

Rebels are piling pressure on the international community to impose a no-fly zone over Libya to cripple Gaddaf's airforce.

While several world powers have backed such a measure, the modalities are yet to be worked out with Hillary Clinton, the US secretary of state, saying such a move should be driven by the United Nations and not the United States.

NATO and the EU are beginning fresh talks on a no-fly zone today.