A heavy bombardment of Tripoli also began after nightfall, with at least nine loud explosions and anti-aircraft fire heard, an Associated Press reporter in the city said.

Earlier in the day, 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 their steps in the first rebel march toward the capital. But this time, the world's most powerful air forces have eased the way by pounding Gadhafi's military assets for the past week.

Sirte is strategically located about halfway between the rebel-held east and the Gadhafi-controlled west along the Mediterranean coast. It is a bastion of support for Gadhafi that will be difficult for the rebels to overrun and the entrances to the city have reportedly been mined. If the rebels could somehow overcome Sirte, momentum for a march on the capital would skyrocket.

An AP reporter at the front said the latest rebel advance during the day reached as far west as the oil port of Ras Lanouf, about 130 miles (210 kilometers) east of Sirte.

After nightfall, Libyan state television confirmed air raids on Sirte and Tripoli. Foreign journalists who were taken by the regime to Sirte a few hours before the bombings began reported hearing at least six loud explosions and warplanes flying overheard. They were driven around the city and said it was swarming with soldiers on patrol and armed civilians, many of them wearing green bandanas that signaled their support for Gadhafi.

In the contested city of Misrata in western Libya, residents reported fighting between rebels and Gadhafi loyalists who fired from tanks on residential areas. Misrata is one of two cities in western Libya that have risen against the regime and suffered brutal crackdowns. It is located between Tripoli and Sirte on the coastal road.