Libyan rebels today rejected an offer by Colonel Muammar Gaddafi to negotiate and said they have captured the eastern town of Bin Jawwad, forcing regime loyalists to flee after days of fighting.

The opposition fighters have threatened to advance westward on the coastal road toward Gaddafi's home town of Sirte if tribal leaders there don't agree to surrender peacefully.

The fighting in the east comes as the rebels consolidated their hold on the capital, Tripoli, some 350 miles to the west of Bin Jawwad.

Mohammed al-Rajali, a spokesman for the rebels on the eastern frontlines, said they captured Bin Jawwad and deployed forces in the city after days of fighting.

He said Gaddafi's forces fled westward and were likely to join regime forces in Sirte, the headquarters of Gaddafi's tribe and his last major bastion of support.

The opposition has threatened to assault the city, which has been heavily targeted by Nato airstrikes, if tribal leaders there refuse a peaceful surrender.

With Gaddafi on the run, his spokesman Moussa Ibrahim called The Associated Press to say Gaddafi is still in Libya and offering to have his son, al-Saadi, lead talks with the rebels on forming a transitional government. In the past, Gaddafi referred to the rebels as "thugs" and "rats."

Ibrahim said he saw Gaddafi on Friday in Libya but would not give more details.

Mahmoud Shammam, the information minister in the rebels' transitional council, rejected the offer.

"I would like to state very clearly, we don't recognise them. We are looking at them as criminals. We are going to arrest them very soon," he said at a news conference. "Talking about negotiations is a daydream for what remains of the dictatorship."

Meanwhile, more signs emerged of arbitrary killings of detainees and civilians by Libyan forces as the rebels swept into Tripoli earlier this week, including some 50 charred corpses found in a makeshift lock-up near a military base that had been run by the Khamis Brigade, an elite unit commanded by Gaddafi's son, Khamis.

Mabrouk Abdullah, who said he survived a massacre by Gaddafi's forces, also told The Associated Press that guards opened fired at some 130 civilian detainees in a hangar near the military base, and fired again when prisoners tried to flee.

Mr Abdullah, who was at the site today, said he and other prisoners were told by a guard they would be released on Tuesday. Instead, guards threw hand grenades and opened fire at detainees huddling in a hangar.

Mr Abdullah said he had been crouching along a wall and was shot in his side, lifting his shirt to show his injury. As survivors of the initial attack tried to flee, they came under fire again, he said.

The killings by Gaddafi troops appeared to have taken place in the past week, as rebel fighters gradually took control of Tripoli, according to a witness and international rights groups.

New York-based Human Rights Watch said today it has gathered evidence indicating that Gaddafi loyalists killed at least 17 detainees and arbitrarily executed dozens of civilians as rebels moved into Tripoli.

Reporters touring Tripoli have found clusters of decomposing corpses in several areas of the capital, including a roundabout near Gaddafi's Bab al-Aziziya stronghold.

"The evidence we have been able to gather so far strongly suggests that Gaddafi government forces went on a spate of arbitrary killing as Tripoli was falling," said Sarah Leah Witson of Human Rights Watch.

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