Moammar Gadhafi's forces on March 5 broke through rebel lines at an opposition-held city that is closest to Tripoli, in a dawn attack that could prove crucial to the regime's defense of the Libyan capital, witnesses said.

They said the forces loyal to the country's longtime leader were inside Zawiya, 30 miles (50 kilometers) west of Tripoli, after overcoming rebel positions with heavy mortar shelling and machinegun fire. They said the shelling damaged government buildings and homes.

The hours-long attack started at dawn. Witnesses said on condition of anonymity that several fires were raging in Zawiya and that heavy black smoke hung over many parts of the city of some 200,000 people. They said snipers were shooting on sight anyone on the streets or residents who venture out on their homes' balconies.

The city's rebels, they said, had retreated to take new positions deeper inside the city. "We will fight them on the streets and will never give up so long as Gadhafi is still in power," said one of the rebel fighters, who also spoke on condition of anonymity for fear of reprisals, The Associated Press reports.