|The town of Ajdabiya is seen as the last defence against Benghazi, the rebel capital [EPA]
As Muammar Gaddafi's forces ratchet up their military offensive against the rebels, shells have fallen six kilometres west of the key Libyan town of Ajdabiya, which the rebels have vowed to defend against government forces.
Journalists for AFP news agency saw two craters of some four metres across and five metres apart near a road junction, after Monday's shelling.
Rebels said there had been no casualties, but the attack on Ajdabiya is seen, from the rebels' viewpoint, "as the last line of defence," said Al Jazeera's Tony Birtley, reporting from the rebel stronghold of Benghazi.
"Gaddafi forces are advancing and It seems that fighting is carrying on and coming close to Benghazi," he said.
"It seems like we are entering the final phase of the conflict but whether this revolution will fail or succeed, that will only be determined in the coming weeks."
Meanwhile, Gaddafi has reportedly offered an amnesty to rebel fighters if they agree to lay down their arms, Libyan state television reported on Monday.
Al Jazeera's correspondent in the capital Tripoli said the offer will play on very anxious rebel forces who don't know how they will be able to put up a fight against Gaddafi's forces, given the overwhelming superiority of his military forces.
"There is an enormous degree of anxiety. It's an all or nothing game now," Anita McNaught said.
"If the rebels do not manage to hold out against Gaddafi and establish some kind of protective zone in the east of the country, it is almost certain in the wake of this there would be some dreadful purge of those who dared to raise their hands against the Gaddafi administration.
"People know that unless they are able to keep Tripoli at bay, that the alternative is almost too awful to contemplate. Those fears apply equally in Tripoli; they are just not expressed as openly as they are in the east."
On the battle field, rebel fighters say they have re-taken parts of the oil town of Brega and captured and even killed Gaddafi troops - but government forces contest that claim, saying that they are in control of the town.
Fighting has also reportedly resumed in the western town of Zuwarah.
A resident said on Monday that government tanks have reached the centre of the rebel held town.
"I am in the centre of Zuwarah. Gaddafi's army is in the centre of Zuwarah now and the tanks are still advancing, I can
see them," Tarek Abdullah told Reuters news agency.
"The fighting with the rebels is still going on," he said.
Gaddafi forces are trying to push back the long stretch of territory controlled by the lightly-armed rebels, who have been pushed back some 200km by superior forces in the past week.