However, residents reported heavy fighting, shelling and explosions in the east and south of Misrata and doctors said Saturday was one of the bloodiest days in weeks.

At least 24 people were killed and 75 were wounded, many of them critically, said a doctor at a Misrata hospital who asked to be identified only by his first name because he was afraid of government retribution. He said that hospital officials who feared a strong attack Saturday had moved out some patients a day earlier to make way for more casualties.

Kaim said the tribal chiefs are determined to put an end to the fighting, in part because it has blocked access to the Misrata seaport. "The leaders of the tribes are determined to find a solution to this problem within 48 hours," he said.

If negotiations fail, "the other option, which is still available for the leaders and the heads of the tribes is a military intervention to liberate Misrata," he said.

He said the six main tribes in the region can muster 60,000 armed men.

Also Sunday, two aid vessels carrying more than 1,400 Misratra evacuees, most of them foreign workers, arrived in the rebel stronghold of Benghazi in eastern Libya. Such ships have been ferrying hundreds of people, including migrant workers and wounded Libyans, from Misrata to Benghazi in recent days.

Between 2,000 and 3,000 people, many of them migrants, are still stranded in the port area of Misrata, awaiting evacuation, said Javier Cepero of the International Committee of the Red Cross.

Some of the migrants have been waiting for rescue for four or five weeks, he said. The Libyan Red Crescent is trying to provide the stranded workers with food and medical care, but sending aid is difficult because of the fighting, he said.