leader Gaddafi's forces pushed into the rebel-held city of Benghazi, defying world demands for an immediate ceasefire.
Explosions shook Benghazi while a fighter jet was heard flying overhead. Residents said the eastern rebel stronghold was under attack from Gaddafi's forces.
"The explosions started about 2 am. Gaddafi's forces are advancing, we hear they're 20 kms from Benghazi," Faraj Ali, a resident, said. "It's land-based fire. We saw one aircraft," he added.
'Attack within hours'
Gaddafi's forces advance into Benghazi before an international meeting today to discuss military intervention in Libya. The meeting will be attended by US Secretary of State Hillary Clinton and Arab leaders.
Libya had declared a ceasefire on Friday after the UN Security Council authorised a no-fly zone over Libya.
But the United States accused Gaddafi of defying international demands for an immediate ceasefire, and France's UN envoy predicted military action within hours of the Paris meeting on Libya on Saturday.
Libyan rebels said they were being forced to retreat by Gaddafi's forces. Black plumes of smoke could be seen on the road to the west of the city, a witness said.
"They can be here in a half hour to 90 minutes," rebel fighter Khalid Ahmed said. "We have no hope in the Western forces," Ahmed added as around him rebel forces pulled back from the advancing frontline.
Elsewhere in the city, rebels also reported skirmishes and strikes by Gaddafi forces.