By Marie-Louise Gumuchian and Ali Shuaib
TRIPOLI, Feb 12 (Reuters) - Saif al-Islam Gaddafi, son and one-time heir apparent of toppled Libyan leader Muammar Gaddafi, will be moved to a Tripoli prison within two months and then face trial, the chairman of Libya's National Transitional Council (NTC) said on Sunday.
Three months after his capture in Libya's Sahara desert dressed as a Bedouin tribesman, Saif al-Islam remains at a secret location in the northwestern town of Zintan, reflecting a wider problem of powerful local militias and a weak central government in the North African country.
In an interview with Reuters, Mustafa Abdul Jalil said authorities were completing the construction of a prison in central Tripoli, begun under the late Muammar Gaddafi, to which Saif al-Islam would be moved.
"At this moment he is being interrogated and his trial will begin as soon as the prison facility is ready," Abdul Jalil said. "I can't give an exact timeframe in terms of weeks or months for this but it will not be more than two months."
Zintan commanders say they have kept Saif al-Islam in their remote mountain town, rather than hand him over to the NTC in Tripoli, to spare him the fate of his father.
The older Gaddafi was killed by his captors shortly after being seized in October, his decomposing body put on public display in a Misrata meat locker before given an inglorious secret burial in the Libyan desert.
Saif al-Islam, a fluent English speaker educated at the London School of Economics, was seen as a the Western-friendly acceptable face of Libya before transforming from liberal reformer to a key figure in his father's fight against rebels seeking his overthrow.
He now faces trial in Tripoli on charges of murder and rape and could face the death penalty if convicted. The International Criminal Court in The Hague has also indicted him for crimes against humanity but Libya says he will be tried in his home country.
"By God's will, Saif al-Islam Gaddafi will receive a fair trial and also all those who are accused in this regard," Abdul Jalil said.
A transitional government appointed in November is leading the country to elections in June but is struggling to restore services and impose order on a myriad of armed groups that toppled Gaddafi after 42 years in power.
And his offspring continue to cast a shadow over the oil-rich North African state.
Abdul Jalil said Niger had confiscated all communication devices belonging to Saif al-Islam's brother Saadi, after he warned of a "coming uprising" in Libya by those opposed to the authorities now in power in Tripoli.
Saadi, who fled south to Niger in September, told Al-Arabiya television by telephone on Friday that he was in regular contact with people in Libya unhappy with the authorities put in place after the ousting and killing of his father.
That prompted Libya to urge Niger on Saturday to extradite Saadi, saying his comments threatened bilateral ties. But Niger said it could not hand over Saadi because he would face execution in Libya.
"First of all, the foreign minister of Niger and the prime minister of Niger were the ones to initiate contact with their counterparts and expressed their apology for what happened," Abdul Jalil said. "I can confirm that the government of Niger has taken all measures and steps to confiscate all communication devices in his possession."
Libya's interim leaders last year approved a request to open an investigation into Saadi over the murder of a footballer who played for the national team in the 1980s.
"The prosecutor general has already sent an extradition request to bring Saadi back to Libya in light of the crime he committed in the field of sports in Libya. The legal and penal procedures in this regard will be followed," he added. (Reporting by Marie-Louise Gumuchian and Ali Shuaib; Editing by Jon Boyle)