By Mohammed Abbas
AJDABIYAH, Libya (Reuters) - Muammar Gaddafi's troops seized the strategic Libyan oil town of Brega on Sunday, forcing rebels to retreat eastward and putting extra pressure on world powers still deliberating on a no-fly zone.
The government offensive had already driven the rebels out of Ras Lanuf, another oil terminal 100 km to the west on the coast road, and the seizure of Brega and its refinery deprived the rebels of more territory and yet another source of fuel.
The government, in a message on state television, said it was certain of victory and threatened to "bury" the rebels, who it linked to al Qaeda and "foreign security services."
A United Nations humanitarian coordinator sent to Tripoli told Reuters he wanted access to areas on both sides of the conflict to assess the impact of the violence on civilians.
On the diplomatic front, France said it would intensify its efforts to persuade world powers to impose a no-fly zone on Libya, where Gaddafi's troops seemed to have gained the initiative in their struggle with rebels seeking an end to his four-decade rule.
Meanwhile Libya said it would welcome an African Union panel that will try to help resolve the crisis, but condemned an Arab League call for a no-fly zone over the country.
"Brega has been cleansed of armed gangs," a Libyan government army source told state television.
Defeated rebel fighters were demoralised
"There's no uprising any more," said rebel Nabeel Tijouri, whose heavy machinegun had been destroyed in the fighting. "The other day we were in Ras Lanuf, then Brega, the day after tomorrow they will be in Benghazi."
Brega is 220 km (135 miles) south of the rebel stronghold of Benghazi and Ajdabiyah is the only sizeable town between the two. From Ajdabiyah there are separate roads to Benghazi and to Tobruk, close to the border with Egypt.
The flat desert terrain means the government's air supremacy and tanks outweigh the rebels' enthusiasm and light weaponry. Only towns and cities provide some cover for the insurgents and, to some extent, lessen the odds against them.
State television carried a confident message from the authorities. "We are certain of our victory, whatever the price," it said.
"Those acts of division will be buried together with those who committed them, who are linked to foreign security services and the terrorist organization al Qaeda," it said.
Rashid Khalikov, the U.N. humanitarian coordinator for Libya, said in an interview he wanted unimpeded access:
"The situation is changing from one day to another," he said. "The main concern is to find out what's going on, which we don't know. There are various reports about the humanitarian impact of recent events. The civilian population is suffering a lot."
The speed of the government advance may overtake drawn-out diplomatic wrangling on whether or how to impose a no-fly zone.
The United States said the Arab League's call for a U.N. no-fly zone to protect Libyan cities was an "important step," but Washington remained cautious about military intervention.
Arab League Secretary-General Amr Moussa said the League had "officially asked the U.N. Security Council to impose a no-fly zone against any military action against the Libyan people."
France said the call demonstrated the willingness of the international community to protect Libyan civilians, and promised to step up its efforts in consultation with the European Union, the Arab League, the U.N. Security Council and the Libyan National Council.
Arab support satisfies one of three conditions NATO set on Friday for it to take on the task of policing Libyan air space. The others are proof that its help is needed, and a U.N. Security Council resolution.
Even if the Security Council meets to discuss a no-fly zone, it is far from clear whether it would pass a resolution as veto holders Russia and China have both publicly opposed the idea.
The Libyan conflict has escalated from a popular uprising similar to protests that toppled the leaders of Tunisia and Egypt and have shaken other countries in the region, and is now more akin to a civil war.
Protests in the capital have stopped.
Human Rights Watch said "Gaddafi and his security forces are brutally suppressing all opposition in Tripoli -- including peaceful protests -- with lethal force, arbitrary arrests, and forced disappearances."
Fresh from crushing the revolt in Zawiyah, west of Tripoli, elite government troops and tanks turned to Misrata, Libya's third biggest city with 300,000 people and the only pocket of rebel resistance outside the east.
Rebels said a mutiny among government troops stalled their advance on Sunday for a second day, but this was impossible to confirm independently.
"From the early morning they (the government troops) are fighting among each other. We hear the fighting," Mohammed, one of the rebel fighters, told Reuters by telephone.
"This division between them came to us from God ... Now we are waiting to see what will happen."
Journalists have been prevented from reaching the city by the authorities. The government dismissed the reports as rumours and said there were al Qaeda fighters in Misrata.
"Some people will give up, some will disappear," said government spokesman Mussa Ibrahim. "Those who stay behind, we will deal with them accordingly."
It took a week of repeated assaults by government troops, backed by tanks and air power, to crush the uprising in Zawiyah, a much smaller town 50 km (30 miles) west of Tripoli.
The death toll in Zawiyah is unknown but much of the town of 100,000 was badly damaged by rocket and tank fire. After fighting ceased there on Friday, one soldier was asked about the fate of the rebels. He made a throat-cutting gesture and laughed.
(Additional reporting by Maria Golovnina and Michael Georgy in Tripoli, Tom Pfeiffer in Benghazi, Mariam Karouny in Ras Jdir, Tunisia, Alister Bull in Washington; Writing by Tim Pearce; Editing by Matthew Jones)