The youngest son of former strongman Suharto was transferred to an Indonesian prison island where he will serve his 15-year sentence alongside his father's golfing buddy.

Hutomo "Tommy" Mandala Putra Suharto was flown Thursday by helicopter to the Nusakambangan prison island off the west coast of Java, an airport official named Bambang in the town of Cilacap told AFP.

An official at the Batu correctional facility on the island confirmed Tommy's arrival following his conviction for murder and illegal weapons possession, but refused further comment.

Batu is where timber tycoon Bob Hassan, the golfing partner and notorious crony of former president Suharto, is serving a six-year jail term for corruption.

Earlier a convoy of armoured vans from the police bomb-squad, their drivers wearing black balaclavas, was seen leaving Cipinang prison in east Jakarta where Tommy had been detained for the past few months, the Antara news agency said. The agency did not know where the convoy, believed to be carrying Tommy, went.

A Jakarta court last month sentenced Tommy for the murder of a supreme court judge who had ordered him jailed 18 months on graft charges, and for the illegal possession of weapons. He made no appeal.

Tommy, who has been detained since November after he was caught, ending a year on the run from the law, has mostly been detained in an upmarket cell, with ensuite bathroom, at Cipinang jail.

The Nusakambangan prison, dating back to the former Dutch colonial era and built between 1908 and 1912, has been used to house prisoners serving long sentences.

Tommy's trial was seen as a key test of Indonesia's corruption-prone legal system and its fledgling democracy. During his father's iron-fisted rule from 1966 to 1998, the rich and powerful were seen to enjoy virtual immunity from the law.