Forces loyal to Libyan leader Moammar Gadhafi have hammered rebels in the west with heavy weapons, as separate fighting creeps toward the capital, Tripoli.

Reporters at the frontline near the western rebel-held town of Zintan say intense fighting Sunday caused damage without immediate report of casualties.

In Zawiyah, 50 kilometers west of Tripoli, Libyan rebels clashed with pro-Gadhafi forces on Saturday. A highway that serves as a major supply route between Tripoli and Tunisia was closed as a result of the unrest. A rebel spokesman told Reuters news agency that fighting there continued Sunday, with government forces getting reinforcements.

Rebels briefly took control of Zawiyah in March but were beaten back by pro-Gadhafi forces.

If the rebels are able to take control of Zawiyah and other towns nearby, they could cut off Tripoli's already-meager supply line. A naval blockade and NATO airstrikes have left the capital largely isolated.

Late Saturday, western news reports said loud blasts from apparent NATO airstrikes rocked the Libyan capital.

Pro-government forces also have rocked the western town of Zlitan as well as the rebel-held city of Misrata, where medical officials say at least 30 people were killed on Friday.

U.S. officials traveling with Secretary of State Hillary Clinton in Africa say Libya's situation will feature prominently in her remarks Tuesday at an African Union meeting in Ethiopia.