Survivors and rights groups say pro-Gadhafi forces committed possible war crimes as rebels moved into the Libyan capital last week, killing scores of detainees and arbitrarily executing dozens of civilians.

Human Rights Watch said Sunday its researchers have documented more than 110 corpses in four locations in Tripoli, many of whom appear to have been killed execution-style either while in detention or with their hands bound.

A metal warehouse in a compound controlled until last week by Libya's elite Khamis Brigade contains about 50 scorched skeletons. A VOA correspondent who visited the structure said another eight bodies lie outside, one with his hands tied behind his back. A survivor said that as rebel forces approached, loyalist soldiers shot their prisoners, then tried to burn the bodies.

Opposition military spokesman Colonel Ahmed Bani said rebels are concerned for the fate of some 40,000 prisoners detained by Mr. Gadhafi's forces who are still unaccounted for. Bani said Sunday that more than 10,000 detainees have been freed from government jails since Tripoli fell last week.

So far, there have been no specific allegations of atrocities carried out by rebel fighters. But the Associated Press reports it remains unclear who is responsible for some of the killings, including those of dozens of dark-skinned men whose bodies were found in two areas of Tripoli.

The gruesome discoveries came as rebels drew closer to leader Moammar Gadhafi's hometown of Sirte, 450 kilometers east of Tripoli. An opposition spokesman said Sunday that anti-government forces would seize the coastal city by force if negotiations with tribal leaders for its surrender failed.

The Sirte region is considered one area where Mr. Gadhafi may have fled to go into hiding. He has dropped out of sight since rebel fighters seized Tripoli.

Earlier, rebels said they had captured the town of Bin Jawad, 150 kilometers east of Sirte, after several days battling loyalist fighters.

A Red Cross ship entered Tripoli harbor Sunday carrying supplies for the city, which saw days of fighting between rebels and Gadhafi supporters last week. A VOA correspondent reported that the capital has widespread shortages of medicine, drinking water and other basic supplies. Many areas are still without electricity.

Libyan rebels earlier gained control of a key border post near Tunisia, and the Reuters news agency reported Sunday that authorities in Tunis had reopened the main Ras Jdir crossing into Libya. Trucks loaded with food and other supplies began to move towards Tripoli, about a two-hour drive away.

In the west, opposition fighters were still battling for control of Zuwarah. Rebels faced stiff resistance from Gadhafi loyalists during efforts to advance into the city, which is on a major supply route into Tripoli.