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 Tripoli, to spare him the fate of his father. 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 being given an inglorious secret burial in the desert.

Saif al-Islam, a fluent English speaker educated at the London School of Economics, was seen as the Western-friendly 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 murder and rape charges and could face the death penalty if convicted. The International Criminal Court in The Hague has 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.

SEEKING SAADI

A transitional government appointed in November is leading the country to elections for a National Assembly in June, but is struggling to 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 state.

Abdul Jalil said Niger had confiscated communication devices belonging to Saif al-Islam's brother Saadi, after Al-Arabiya broadcast an interview with him on Friday.

In the telephone interview Saadi, who fled south to Niger in September, said he was in regular contact with people in Libya unhappy with authorities and warned of a coming uprising in the country.

That prompted Libya to urge Niger 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.

DISARMING FIGHTERS

As it seeks to restore order, Libya's government hopes to amalgamate militias into the police and national army but the process has been slow.

The progress of this programme has not been as we had hoped for as we wanted them to join as individuals not as groups, Abdul Jalil said. About 10 percent have joined the security bodies and handed over their weapons.

Authorities are also investigating reports by rights groups that former rebels are torturing detainees in makeshift prisons. Abdul Jalil said committees had been established to look into this: They will soon finalise their tasks. There will be judicial procedures in this regard.

He said there were plans to move residents of Tawergha, now living in refugee camps, back to their town. Gaddafi's forces used Tawergha as a base to besiege and shell Misrata during the war. Its residents, mainly black Libyans, say they were held hostage by Gaddafi's men and did not collaborate.

Human Rights Watch has said Misrata rebels have looted and destroyed homes in Tawergha and neighbouring farming villages and revenge attacks against refugees and arbitrary arrests continue. Families and children will be returned to their homes as soon as those who are wanted face justice, Abdul Jalil said.

In October, he said he wanted the new order to be based on Islamic sharia law. Asked about an Islamic financial system in Libya, he said: This is one of the basic principles of Islam and I believe that the international financial crisis that is sweeping the whole world is caused by usury.

Asked about his own longer term plans, he said: My life after the National Assembly elections will be devoted to reconciliation teams in the field of national reconciliation only.

(Reporting by Marie-Louise Gumuchian and Ali Shuaib; Editing by Jon Boyle and Ben Harding)