By Angus MacSwan and Maria Golovnina
NAWFALIYAH/MISRATA, Libya (Reuters) - Rebels advanced west toward the birthplace of Libyan leader Muammar Gaddafi on Monday, firing mortars and heavy machineguns in sporadic clashes with loyalist forces.
Emboldened by Western-led air strikes against Gaddafi's troops, rebels took the town of Nawfaliyah and moved toward Sirte, Gaddafi's home town and an important military base, in the sixth week of an uprising against his 41-year rule.
As rebels pressed forward in the east, Gaddafi's troops were patrolling an area near the center of Misrata after shelling the previously rebel-controlled western city for days and Arab news networks reported Western air strikes in the west of Tripoli.
The government in Tripoli said it had "liberated" Misrata from rebels and declared a ceasefire there.
Diplomatic activity accelerated on the eve of a 35-nation meeting in London on Tuesday to discuss the crisis in the oil-producing North African desert state.
Italy proposed a deal including a ceasefire, exile for Gaddafi and dialogue between rebels and tribal leaders. The rebel leadership ruled out compromise with Gaddafi's followers.
"We have had a vision from the very beginning and the main ingredient of this vision is the downfall of the Gaddafi regime," spokesman Hafiz Ghoga told reporters in the rebel stronghold of Benghazi in eastern Libya.
Qatar became the first Arab country to recognize the rebels as the sole legitimate representative of the Libyan people, in a move that may presage similar moves from other Gulf states. Libyan state television called the move "blatant interference".
Russia criticized the Western intervention that has turned the tide in the conflict, saying it amounted to taking sides in a civil war and breached the terms of a United Nations Security Council resolution.
U.S. SAYS REBELS NOT ROBUST
U.S. Vice Admiral Bill Gortney said on Monday the rebels fighting Gaddafi were not robust and the gains they have made on the battlefield in recent days were tenuous.
Gortney, director of the U.S. military's Joint Staff, said the United States was not directly supporting the opposition but it had achieved a military benefit from coalition air strikes.
He said the United States had no confirmed report of any civilian casualty caused by coalition forces and that coalition had fired six Tomahawk cruise missiles in the past 24 hours and had carried out 178 air sorties.
The French and British leaders called for supporters of Gaddafi to abandon him and asked Libyans opposing him to join a political process to pave the way for his departure.
"Gaddafi must go immediately," President Nicolas Sarkozy and Prime Minister David Cameron said in a joint statement. "We call on all his supporters to drop him before it is too late."
In the nine days since the start of the Western-led bombing, the motley volunteer force of rebels has pressed half-way along the coast from its stronghold of Benghazi toward Tripoli and regained control of major oil terminals in the OPEC state.
A U.S. Treasury Department official said rebels could sell Libyan crude without being subject to U.S. sanctions if they conducted the transactions outside entities in Gaddafi's administration subject to sanctions.
With its finances under pressure, the rebel leadership said it hopes to restart oil exports within a week. Some energy traders said that, sanctions aside, they could not touch Libyan oil because of shipping and legal risks.
On Monday rebels met sporadic resistance as they pushed their advance in convoys of pick-up trucks with machineguns.
Just west of sandy, barren Nawfaliyah, bursts of sustained machinegun fire and the whoosh of several rockets could be heard, and plumes of black smoke rose ahead.
"Those are from our guns," said Faisal Bozgaia, 28, a hospital worker turned rebel fighter, pointing to the smoke.
ADVANCE STRETCHES SUPPLY LINES
Rebels said occasional ambushes by Gaddafi forces had pushed them back but that they later regained their positions.
"We are advancing one, two kilometers at a time," rebel Khalif Ali, 22, said in the town of Harawah, west of Nawfaliyah.
But the rapid advance is stretching rebel supply lines.
"We have a serious problem with petrol," said a volunteer fighter waiting to fill up in the oil town of Ras Lanuf.
Reuters correspondent Michael Georgy, reporting from Sirte to the west, saw police and military but no sign of fighting.
Soldiers were manning checkpoints and green Libyan flags flapped in the wind. Militiamen fired AK-47 rifles defiantly into the air. "If they come to Sirte, we will defend our city," said Osama bin Nafaa, 32, a policeman.
In Misrata, Gaddafi soldiers manned checkpoints and took up position on rooftops. Some housefronts were smashed, smoke was rising from several areas and gunfire rang out across the city.
Several civilians approached a group of journalists, some of them woman and children waving green flags. "Misrata is ours, there are still some bad guys in other parts, but Gaddafi is winning, the city is ours," resident Abduq Karim said.
"Civilians are happy," said an army official who declined to be named. "Everything you are hearing is a lie. The function of our army is to save the people and to protect the leader. We cannot kill our own people."
A rebel spokesman in another western town, Zintan, said forces loyal to Gaddafi had bombarded the town with rockets early on Monday, Al Jazeera reported.
Western-led air strikes began on March 19, two days after the U.N. Security Council authorized "all necessary measures" to protect civilians from Gaddafi's forces.
But from the outset, the mission faced questions about its scope and aims, including the extent to which it will actively back the rebel side and whether it might target Gaddafi himself.
The start of allied bombings proved a turning point for the rebels who were hemmed into Benghazi at the time.
RUSSIA ACCUSES WEST
Russia, which abstained in the U.N. vote, said Western attacks on Gaddafi forces amounted to taking sides.
"We consider that intervention by the coalition in what is essentially an internal civil war is not sanctioned by the U.N. Security Council resolution," Foreign Minister Sergei Lavrov told a news conference.
NATO chief Anders Fogh Rasmussen told the BBC: "We are there to protect civilians -- no more, no less."
France, which dropped the first bombs of the campaign nine days ago, said the coalition was strictly complying with U.N. terms. It said its warplanes struck a command center south of Tripoli belonging to Gaddafi's forces on Sunday and Monday.
The Defense Ministry in London said British Tornado aircraft destroyed Libyan government ammunition bunkers in the Sabha area of Libya's southern desert in the early hours of Monday.
On Sunday, NATO agreed to take full command of military operations in Libya after a week of heated negotiations.
The United States, which led the initial phase, had sought to scale back its role in another Muslim country after the wars in Iraq and Afghanistan. An alliance spokeswoman said on Monday the transition would take a couple of days.
Libya accused NATO of "terrorizing" and killing its people as part of a global plot to humiliate and weaken it.
A Libyan government spokesman said on Monday night that Western air strikes in Sabha, 700 km (420 miles) south of Tripoli, killed 12-13 civilians the night before. Libyan television reported an air strike on Surman, west of Tripoli.
The government says the Western-led air attacks have killed more than 100 civilians, a charge denied by the coalition which says it is protecting civilians from Gaddafi forces and targeting only military sites to enforce a no-fly zone.
(Additional reporting by Alexander Dziadosz, Edmund Blair, Maria Golovnina, Michael Georgy, Ibon Villelabeitia, Lamine Chikhi, Mariam Karouny, Joseph Nasr, Marie-Louise Gumuchian and Steve Gutterman; Writing by Mark Trevelyan and Tom Pfeiffer; Editing by Peter Millership)