* Main rebel checkpoint now 15-20 km east of Ras Lanuf
* Blasts heard, smoke plumes seen rising around town
* Other oil towns targetted, oil facilities in one hit
By Mohammed Abbas and Alexander Dziadosz
NEAR RAS LANUF, Libya, March 11 (Reuters) - Libyan rebels withdrew their last main checkpoint to the east of Ras Lanuf on Friday after forces loyal to Muammar Gaddafi launched a withering land, sea and air offensive to retake the oil town.
Rebels at the checkpoint that is now 15-20 km (10-13 miles) east of the town they had controlled until Thursday said their forces were still fighting with Gaddafi's troops in the centre.
"This is our last checkpoint, ahead are clashes. The clashes are in the residential area," rebel Youssef Mohannad said.
A Reuters correspondent heard sounds of blasts and saw plumes of smoke rising in the direction of Ras Lanuf and also heard the sporadic rattle of machine gun fire, a day after Gaddafi's forces launched air strikes and moved tanks in.
Government troops were also landed by sea in the coastal town, about 590 km (370 miles) east of Tripoli, rebels said.
Libyan state television said Gaddafi's troops now controlled Ras Lanuf, showing a group of soldiers celebrating just outside. But the fate of the town was still unclear on Friday.
To the east, near the town of Uqaylah, a warplane launched an air strike in the desert on Friday, witnesses said. A rebel spokesman said another air strike had hit Brega, a rebel-held oil town even further east. That strike could not be confirmed.
A rebel drive west has been stopped in its tracks and sent into reverse by Gaddafi's superior firepower after rebels had reached Bin Jawad, about 60 km (40 miles) west of Ras Lanuf.
Some young fighters, speaking a few kms (miles) from the frontline, remained upbeat. "War is always backwards and forwards. God willing, we go forwards again," said rebel Jomaa Irjai, 22, clutching his AK-47 Kalashnikov rifle.
But closer to the front, the strain of fighting showed after rebels, mostly riding on 4x4 pick-ups with anti-tank and aircraft guns, rocket propelled grenade launchers and rifles, were thrown back by Gaddafi's warplanes, tanks and artillery.
"Where is the West? How are they helping? What are they doing" shouted one angry fighter, while another frustrated rebel responded to a question about the latest events saying: "Why don't you go and ask Gaddafi's forces they are just over there."
Rebels have called for the West and other powers to set up a no-fly zone to ground Gaddafi's planes and for targetted air strikes to protect them. They have been frustrated by the failure of the United States and others to move quickly.
A Reuters correspondent on Thursday saw rebels fire from multiple rocket launcher from one army truck and on Friday rebels were seen moving two tanks and three armoured personnel carriers towards Ras Lanuf. But they are still outgunned.
Rebels had enthusiastically welcomed reporters on the front on earlier days, but have become increasingly wary of their presence, blaming the media for disclosing rebel positions.
"There are no photos of Gaddafi's forces. When the media photographs our forces they give away what we have and where we are, and that is why we got pushed back," said rebel Mohamed al-Houni before telling the Reuters correspondent to leave.
There are no foreign media working with the same kind of freedom of movement on the frontline with Gaddafi's forces. Images are generally restricted to state TV, choreographed tours for visiting foreign reporters or shakey video grabbed by mobile phones and sent out to the world by ordinary Libyans.
State television showed images on Friday of a group of Gaddafi's troops with light arms outside an entrance to Ras Lanuf waving the nation's green flag. On an arch above the gate nearby was written "The town of Ras Lanuf welcomes you."
"God willing, we will be victorious," one woman shouted from a car to a state television reporter, another civilian told the television that Ras Lanuf was "under the complete control of our forces", a reference to Gaddafi's troops. The location of those images was not clear.
But a concerted offensive during Thursday and Friday still did not appear to deliver Ras Lanuf into government hands even if rebel forces were being pressed hard.
Rebel fighter Ibrahim al-Alwani had told Reuters by telephone earlier on Friday that he and comrades were still in Ras Lanuf but had seen government troops in the centre. "I saw maybe 150 men and three tanks," he said. "I can hear clashes."
Mohammed al-Mughrabi, who described himself as a spokesman for the rebels but declined to give his exact location, said by phone that government troops had landed by boat near the Fadeel hotel in Ras Lanuf, where clashes were in progress.
"Four boats carrying 40 to 50 men each landed there. We are fighting them right now," he said. A fighter in Brega said comrades in Ras Lanuf reported government forces had entered by boat and in tanks. Government warplanes and gunboats bombarded rebel positions on Thursday. (Writing by Edmund Blair in Cairo; editing by Giles Elgood)