International air raids have targeted Muammar Gaddafi's home town of Sirte for the first time as rebels made a high-speed advance toward the regime stronghold, a formidable obstacle that must be overcome for the government opponents to reach the capital Tripoli.
A heavy bombardment of Tripoli also began after nightfall on Sunday, with at least nine loud explosions and anti-aircraft fire heard.
Earlier rebels regained two key oil complexes along the coastal highway that runs from the opposition-held eastern half of the country toward Sirte and beyond that, to the capital.
Moving quickly westward, the advance retraced the steps of the rebels' first march toward the capital. But this time, the world's most powerful air forces have eased the way by pounding Col Gaddafi's forces for the past week.
Sirte is strategically located about half way between the rebel-held east and the Gaddafi-controlled west along the coastal highway.
It is considered a bastion of support for Col Gaddafi that will be difficult for the rebels to take and the entrances to the city have reportedly been mined.
After nightfall, loud explosions and warplanes flying overhead were reported in Sirte. They said the city was swarming with soldiers on patrol. Libyan state television confirmed air raids on Sirte and Tripoli.
In Washington, Defence Secretary Robert Gates said he could not offer a timetable for how long the Libya operation could last, as the Obama administration tried to bolster its case for bringing the US into another war in the Muslim world.
The UN Security Council authorised the operation to protect Libyan civilians after Gaddafi launched attacks against anti-government protesters who demanded that he step down after nearly 42 years in power.
The air strikes have crippled Gaddafi's forces, allowing rebels to advance less than two weeks after they had seemed at the brink of defeat.