Col Gaddafi's fugitive spy chief Abdullah al-Sanussi has been captured, Libya's interim government says.He was seized by fighters in the south of the country, officials say.Mr Sanussi, who has not yet been seen in custody, was one of the last senior figures from the Gaddafi regime still on the run.Gaddafi's son Saif al-Islam was seized on Saturday. Both he and Mr Sanussi are wanted for alleged war crimes by the International Criminal Court (ICC).Mr Sanussi, a brother-in-law of Col Gaddafi, is said to have been arrested at his sister's home in the southern town of Sabha on Sunday.He was regarded as the late leader's right-hand man - and one of the regime's most-feared figures.Mr Sanussi, 62, is being sought by the ICC in connection with the repression of protests against Gaddafi's rule earlier this year.He has also been accused of human rights abuses, including his implication in the massacre in 1996 of more than 1,000 inmates at the Abu Salim prison in Tripoli.'Fair trial'Mr Sanussi was a close adviser to Saif al-Islam Gaddafi, according to leaked US embassy documents.Saif al-Islam is due to be interrogated by prosecutors at a secret location in the western city of Zintan, where he was taken by militiamen who seized him in Libya's southern desert.The commander of the Zintan militia told the BBC their prisoner was being well-treated at a private house, and had seen a doctor on Sunday about a wound to his hand.The commander also gave details of the capture on Saturday. He said Saif al-Islam had asked to be shot dead but the militias refused.The interim government has indicated it wants to try him in Libya, and interim Prime Minister Abdurrahim al-Keib said he would receive a fair trial.Concerns have been raised about the possibility of ill-treatment, after what happened to Gaddafi following his capture in Sirte last month.ICC prosecutor Luis Moreno Ocampo is to visit Libya to discuss the handling of the case of Saif al-Islam. He is expected to request his extradition to the Hague.Mr Ocampo has said that while national governments had the first right to try their own citizens for war crimes, his primary goal was to ensure a fair trial.BBC Middle East correspondent Jon Leyne says allowing Saif al-Islam to be taken out of Libya would be hugely unpopular there and, quite possibly, his Zintan captors would refuse to hand him over.