By Maria Golovnina and Alexander Dziadosz
TRIPOLI/RAS LANUF, Libya (Reuters) - Libyan government forces attacked rebels with rockets, tanks and warplanes on western and eastern fronts, intensifying their offensive to crush the revolt against Muammar Gaddafi.
Rising casualties and the threats of hunger and a refugee crisis increased pressure on foreign governments to act, but they struggled to agree a strategy for dealing with the turmoil, many fearful of moving from sanctions alone to military action.
In besieged Zawiyah, the closest rebel-held city to Tripoli, trapped residents cowered from the onslaught on Tuesday.
"Fighting is still going on now. Gaddafi's forces are using tanks. There are also sporadic air strikes ... they could not reach the center of the town which is still in the control of the revolutionaries," a resident called Ibrahim said by phone.
In the east, much of which is under rebel control, warplanes bombed rebel positions around the oil port of Ras Lanuf.
Rebel euphoria seemed to have dimmed. "People are dying out there. Gaddafi's forces have rockets and tanks," Abdel Salem Mohamed, 21, told Reuters near Ras Lanuf. "You see this? This is no good," he said of his light machinegun.
The rebel leadership said that if Gaddafi stepped down within 72 hours it would not seek to bring him to justice.
Earlier, the rebels said they had rejected an offer from the Libyan leader to negotiate his surrender of power. The government called such reports "absolute nonsense."
Britain and France led a drive at the U.N. for a no-fly zone which would prevent Gaddafi from unleashing air raids or from flying in reinforcements. The Arab League and several Gulf states have also called for such a step.
"It is unacceptable that Colonel Gaddafi unleashes so much violence on his own people and we are all gravely concerned about what would happen if he were to try to do that on an even greater basis," British Foreign Secretary William Hague said.
Russia and China, who have veto power in the U.N. Security Council, are cool toward the idea of a no-fly zone.
The U.S. government, whose interventions in Iraq and Afghanistan enraged many of the world's Muslims, said it was weighing up military options and that action should be taken only with international backing.
Rebels still controlled the central square of Zawiyah, 50 km (30 miles) west of Tripoli, and were using loud hailers to urge residents to help defend their positions, said a witness, a Ghanaian worker who fled the town on Tuesday.
A government spokesman said troops were now in control but a small group of rebel fighters was still putting up resistance.
"Maybe 30-40 people, hiding in the streets and in the cemetery. They are desperate," he told Reuters in Tripoli.
A Libyan man who lives abroad said he spoke by phone on Tuesday to a friend in Zawiyah who described desperate scenes.
"Many buildings are completely destroyed, including hospitals, electricity lines and generators," he said.
"People cannot run away, it's cordoned off. They cannot flee. All those who can fight are fighting, including teenagers. Children and women are being hidden."
Tanks were firing everywhere, he said.
The reports could not be verified independently as foreign correspondents have been prevented from entering Zawiyah and other cities near the capital without an official escort.
Air strikes hit at rebels behind the no-man's land between the coastal towns of Ras Lanuf and Bin Jawad, 550 km (340 miles) east of Tripoli and the site of oil terminals.
One strike smashed a house in a residential area of Ras Lanuf, gouging a big hole in the ground floor.
Mustafa Askat, an oil worker, said one bomb had wrecked a water pipeline and this would affect water supplies to the cit
"We have a hospital inside, we have sick people and they need water urgently," he said.
A convoy from the U.N. food agency was scheduled to reach the rebel-held port of Benghazi on Tuesday to deliver the first food aid in Libya since the revolt erupted three weeks ago.
The rebel army -- a rag-tag outfit largely made up of young volunteers and military defectors -- made swift gains in the first week of the uprising which saw them take control of the east and challenge the government near Tripoli.
But their momentum appears to have stalled as Gaddafi's troops have pushed back with heavy weapons.
Rebels said government forces had dug in their tanks near Bin Jawad while rebels retreated to Ras Lanuf. The two towns are about 60 km (40 miles) apart on the strategic coastal road along the Mediterranean sea.
The emerging front line divides the country along ancient regional lines, with key oil facilities stuck in the middle.
Gaddafi has denounced the rebels as drug-addled youths or al Qaeda-backed terrorists, and said he will die in Libya rather than surrender.
"If he leaves Libya immediately, during 72 hours, and stops the bombardment, we as Libyans will step back from pursuing him for crimes," Mustafa Abdel Jalil, head of the rebel National Libyan Council, told Al Jazeera television.
The Libyan uprising is the bloodiest of a tide of protests against autocratic rulers in North Africa and Middle East which has already seen the leaders of Tunisia and Egypt dethroned.
The phenomenon has left the West struggling to formulate a new direction for a region that sits on vast reserves of oil.
Brent crude dropped to below $113 per barrel on Tuesday before creeping back to $114.00 by 1400 GMT.
(Additional reporting by Michael Georgy in Tripoli, Alexander Dziadosz in Ajdabiya, Mohammed Abbas in Ras Lanuf, Stefano Ambrogi in London, Writing by Andrew Roche: Editing by Giles Elgood)