Forces loyal to Libyan leader Moamar Gaddafi have been attacking the town of Ajdabiya, the last major population centre before the rebel stronghold of Benghazi.
Rebel fighters in Ajdabiya said four shells had hit west of the town while a former officer who defected from Mr Gaddafi’s air force said there had been air strikes.
The town is crucial to allowing government forces to besiege the rebels in Benghazi by cutting off their lifeline to the east and the Egyptian border.
Two key highways run out of Ajdabiya; one goes along the coast to Benghazi, and the other cuts across the desert to Tobruk.