Muammar Gaddafi's son and one-time heir apparent Saif al-Islam has been detained in the southern desert, Libya's interim justice minister and other officials have said.

Fighters from the western mountain city of Zintan announced his capture on Saturday as gunfire and car horns marked jubilation across the country at the arrest of the British-educated 39-year-old who a year ago seemed set to follow his father as Libya's leader.

Saif al-Islam and three armed companions were taken without a fight during the night, officials said. Gaddafi's son was reportedly not injured, unlike Gaddafi himself, who was killed last month after being captured by fighters in his home town of Sirte.

Libyan Prime Minister Abdul Raheem al-Keeb officially announced the capture of Saif al-Islam Gaddafi during a news conference on Saturday evening, assuring Libyans and rest of the world he will face a fair trial.

"Because of this historic occasion, I would like to congratulate the men and women of Libya and the rebels of Libya, for their struggle, determination and heroism, which gave way to such victory," al-Keeb said to a cheering audience.

'Proper justice'

The prime minister also said he has confidence in Zintan authorities to take care of Saif al-Islam until he gets "proper justice" and a fair trial.

A man who appeared to be Saif al-Islam Gaddafi, but whose identity was unconfirmed, was flown by Libyan militiamen to the town of Zintan in the northwest of Libya on Saturday, a Reuters news agency correspondent, who was on the plane, said.

The unidentified man wore traditional robes with a scarf pulled over his face. The man's thumb, index finger and another finger were heavily bandaged.

Saif al-Islam Gaddafi told Reuters that he was feeling fine. Asked by the correspondent if he was feeling all right, Gaddafi said simply: "Yes."

Reluctant to speak at length, Saif al-Islam was asked about bandages on the thumb and two fingers of his right hand.

"Air force, air force," he said. Asked if that meant a NATO air strike, he said: "Yes. One month ago."

Aides to Gaddafi had said his motorcade was caught by a NATO air strike as he tried to flee the pro-Gaddafi stronghold of Bani Walid on October 19, the day before his father was captured.

After the brief exchange with the heavily bearded prisoner, Libyan Reuters journalists who have met Saif al-Islam said they had no doubt that was indeed him, although he repeatedly declined to confirm his identity outright.

So large was the crowd that greeted the Soviet-built cargo aircraft that flew in that his captors removed four other prisoners and other people from the plane, leaving Saif al-Islam on board on the tarmac.

The Zintan fighters who claimed to have captured Saif al-Islam said they planned to keep him detained in Zintan until there was an administration to hand him over to.

Abdurrahim El-Keib, the interim prime minister, is scheduled to form a government by Tuesday. The fate of Saif al-Islam, who Libyans want to try at home before possibly handing him over to the ICC, will be an early test of the fledgling government's authority.

Muammar Gaddafi's beating, abuse and ultimate death in the custody of former rebel fighters was an embarrassment to the previous transitional government. Officials in Tripoli said they were determined to handle his son's case in a more orderly manner.

PHOTO CAPTION

Saif al-Islam Gaddafi (L) is pictured standing in a plane in Zintan November 19, 2011.

Al Jazeera