Warplanes have dropped missiles near rebel positions in the desert east of Ras Lanuf, witnessed by reporters for the AP and AFP news agencies.
There were no immediate reports of casualties.
Rebels fighting to oust Col Gaddafi after 41 years in power took Ras Lanuf on Friday.
Meanwhile, a rebel spokesman said a representative for Col Gaddafi had offered to hold talks on the Libyan leader's exit.
The rebels rejected the offer, the spokesman said.
There has been no comment from Col Gaddafi's government on the rebels' statement, but the Libyan leader has refused to cede power in the past.
He argues that he has no official position, and therefore it is impossible for him to resign.
The BBC's Wyre Davies, in Tripoli, says Col Gaddafi's side believe they are making significant military gains, consolidating their hold on western Libya.
It is difficult to see how the Gaddafi regime would in any mood to compromise or talk about succession, he says.
Meanwhile, Western powers are stepping up their efforts to put in place a no-fly zone over Libya.
Britain and France are drafting a UN resolution, which will be debated by Nato defence ministers on Thursday.