Col Muammar Gaddafi still poses a danger for Libya and the world, the head of the Libyan rebels has said.National Transitional Council (NTC) head Mustafa Abdul Jalil said Nato and other allies must continue supporting rebels against the "tyrant".The rebels have taken the small town of Nofilia on their way to the Gaddafi stronghold - and hometown - of Sirte.Col Gaddafi's whereabouts remain unknown since rebels swept into Tripoli last week, capturing his compound.They already control most of Libya, after months of clashes since the first protests began.Speaking at a meeting of defence chiefs in Qatar, the NTC's head, Mustafa Abdul Jalil, said Col Gaddafi's forces could still wage brutal counter-attacks even as rebel forces pushed into the last pockets of resistance by pro-Gaddafi troops."Gaddafi's defiance of the coalition forces still poses a danger, not only for Libya, but for the world. That is why we are calling for the coalition to continue its support," Mr Jalil said at the meeting in Doha.Rebels say they are in talks with Sirte's tribal elders to avoid bloodshed, but so far they have been unsuccessful.It may be that tribal leaders have fresh in their minds the warning Col Gaddafi broadcast last week, to the effects that rebels are converging on the town to loot and rape the women, reports the BBC's Paul Wood who is with the rebels headed towards Sirte.Or perhaps, as one rebel officer said, the tribal leadership wanted to surrender, but were being stopped from doing so by the thousands of soldiers thought to be in the town, our correspondent says.So with Nato jets flying missions in support, the rebels expect shortly to fight what may well be the last big battle of this war and of their revolution, he adds.Nato has said it remains committed to the operation.The Nato mandate continues until the end of September when it would have to reviewed by a meeting of all its members. Prisoners' concernsA ship carrying hundreds of prisoners, released from Libyan jails, has arrived in Benghazi from Tripoli.In scenes of almost delirious joy, they were greeted and hugged by wives, husbands, brothers, sisters and friends, says the BBC's Jon Leyne who watched as the ship arrived in the rebel city.Some had been captured by Col Gaddafi's forces during the last six months; others had been held for years.They spoke of torture, beatings and starvation rations.Rebel leaders have spoken of their concerns for tens of thousands of others - taken prisoner in the past few months - who are still missing.The rebels say they fear their bodies could be unearthed in mass graves, or that the prisoners have been abandoned in secret, underground military bunkers.Key prison records and other documents are at risk of being lost as sites remain unsecure and documents destroyed or taken away in Libya, Amnesty International has warned, urging the NTC to preserve such documents.These records could be critical for any forthcoming trials for crimes committed under the rule of Col Muammar Gaddafi, or to shed light on the fate of the many prisoners who have "disappeared" in Libyan prisons in the last few decades, Amnesty said.