TRIPOLI (Reuters) - Troops loyal to Libyan leader Muammar Gaddafi intensified their counter-offensive on Friday to retake ground from out-gunned insurgents who appealed to foreign powers to impose a no-fly zone to stop the onslaught.

Government forces, with air supremacy and a big advantage in tanks, appear to have regained the momentum in the three-week old conflict and if their push proceeds apace it could overtake sluggish international efforts to halt Gaddafi.

The sound of explosions and small arms fire came from Ras Lanuf on Friday as government troops landed from the sea backed by tanks and air power fought to recapture the oil port town.

"Four boats carrying 40 to 50 men each landed there. We are fighting them right now," rebel spokesman Mohammed al-Mughrabi said, but he declined to say exactly where he was.

Rebel fighter Ibrahim al-Alwani said he and his comrades were still in the residential area of Ras Lanuf and had seen government troops in the town center.

"I saw maybe 150 men and three tanks," he said.

Insurgents withdrew their last main checkpoint in Ras Lanuf on Friday, setting it up 15-20 km (10-13 miles) to the east.

"This is our last checkpoint, ahead are clashes. The clashes are in the residential area (of Ras Lanuf)," rebel fighter Youssef Mohannad told Reuters at the checkpoint.

As multiple international bodies agonise over whether, or how to impose a no-fly zone, Gaddafi's warplanes carried out an air strike behind enemy lines near Uqaylah, witnesses said, and rebels reported another bombing further east near Brega.

The insurgents were angry at the international inaction.

"Where is the West? How are they helping? What are they doing," shouted one angry fighter.

West of Tripoli, the revolt in Zawiyah appeared all but crushed, with rebels clinging to only parts of the shattered city. Residents described scenes of carnage, with women and children among the dead, but the city was calm on Friday.

"This is the calm before the storm," a fighter named Ibrahim told Reuters by telephone.

"All we want is a no-fly zone. To ban him (Gaddafi) from flying his planes. I swear to God, if this happens we will be talking to you from Bab al-Aziziyah in a week," he said, referring to Gaddafi's compound in the Libyan capital.

The only other rebel holdout in western Libya, Misrata about 200 km (125 miles) east of Tripoli, was also for now calm.

"Revolutionaries are ready to counter the militia and I expect clashes in the coming hours," a resident, Abdelbasset, told Reuters by telephone.

Gaddafi's son Saif al-Islam told the rebels they faced a full-scale assault to crush their uprising which began after Hosni Mubarak was overthrown in neighbouring Egypt a month ago.

"It's time for action. We are moving now," he told Reuters in an interview on Thursday. He said the government had given the rebels two weeks for negotiations. "Time is out now."


As EU heads of government prepared to meet in Brussels on Friday, Libya's insurgent leader warned any delay in imposing a no-fly zone could let Gaddafi regain control.

"We ask the international community to shoulder their responsibilities," Mustafa Abdel-Jalil, head of the National Libyan Council, told the BBC.

"The Libyans are being cleansed by Gaddafi's air force. We asked for a no-fly zone to be imposed from day one, we also want a sea embargo," he said. "We urgently need some arms and we also need humanitarian assistance and medicines to be sent to the cities besieged by Gaddafi troops."

British Prime Minister David Cameron said the European Union must step up measures to isolate Gaddafi. French President Nicolas Sarkozy has already recognised the Libyan National Council as the legitimate authority, and he and Cameron urged the EU to do the same.

"Recognition, as the French have done, in effect paves the way for more open assistance. Once you've done that, you've cast in your lot with the rebels, and you might as well go further and arm them," said Shashank Joshi, associate fellow at Britain's Royal United Service Institute.

The arms embargo on Libya should apply to the rebels as well as the government, "but in practice legal limitations may be being ignored and lethal equipment may already being supplied," Joshi said.

The Arab League is holding an emergency session on Libya on Saturday, but it is not clear if it can agree on action due to likely Syrian objections. Gulf Arab states, all members of the Arab League, said on Thursday Gaddafi's government was no longer legitimate and called on the League to impose a no-fly zone.

The African Union, long courted by Gaddafi, rejected foreign intervention, but said it was sending a delegation of five heads of state to Libya soon to try to arrange a truce.

In practice, any military action will require the participation of the United States which, along with NATO, has expressed doubt over the wisdom of imposing no-fly zones without full international backing and a legal justification.

U.S. National Intelligence chief James Clapper said Gaddafi was "in this for the long haul" and was likely to prevail.

(Additional reporting by Mohammed Abbas in Brega, Tom Pfeiffer in Benghazi, Luke Baker, David Brunnstrom, Missy Ryan and Lucien Toyer in Brussels, Paul Eckert and Tabassum Zakaria in Washington, Stefano Ambrogi and Olesya Dmitracova in London, John Irish in Paris, Stephanie Nebehay in Geneva, Harry Papachristou in Athens; Writing by Andrew Dobbie and Jon Hemming; Editing by Giles Elgood)