Libyan state television reports that international airstrikes are targeting Muammar Gaddafi's hometown and stronghold of Sirte for the first time.
Foreign journalists in the city reported loud explosions and warplanes flying overheard.
Sirte is strategically located about halfway between the rebel-held east and the Gaddafi-controlled west along a key coastal highway. Rebels were advancing rapidly west on the highway Sunday toward Sirte after international airstrikes eased their way.
An Associated Press reporter in the capital said international forces were also heavily bombarding the city that is Gaddafi's main support base. There were at least nine loud explosions in Tripoli after nightfall and anti-aircraft fire was heard.
Anti-aircraft fire has been heard in Libya's capital Tripoli after dark, signaling that another round of international airstrikes on Muammar Gaddafi's regime is under way.
Residents in the contested city of Misrata in western Libya reported fighting Sunday between anti-government rebels and pro-Gaddafi forces firing from tanks on residential areas.