Chhouk Rin was detained near an old Khmer Rouge base where Australian David Wilson, Briton Mark Slater and Frenchman Jean-Michel Braquet were imprisoned and killed.

They were abducted in July 1994 when a band of guerrillas ambushed their train en route from Phnom Penh to the seaside town of Sihanoukville.

The rebels killed at least 10 Cambodians in the attack before marching the three backpackers and several other passengers to the Khmer Rouge's southern base at Vine Mountain.

Shallow grave

The backpackers, all in their 20s, were killed several months later after negotiations for their release broke down.

Their bodies were found buried in shallow graves when the army stormed the base.

The Khmer Rouge commander at Vine Mountain, Nuon Paet, was jailed for life last October for his role in the slayings.

Military police chief General Sao Sokha said Chhouk Rin was arrested at his home on Monday and was now in prison in the capital Phnom Penh.

Chhouk Rin was one of the first prominent Khmer Rouge figures to defect during the long civil war and was rewarded with a senior army position.

A third Khmer Rouge commander, Sam Bith, who is now a general in the army, has also been charged with the killings, but has not yet been arrested.

During his trial, Nuon Paet, said it was Sam Bith who had ordered the tourists to be slaughtered.

Tribunal

An estimated 1.7 million Cambodians died during the Khmer Rouge's reign of terror in the late 1970s.

Chhouk Rin's arrest comes as Cambodia and the United Nations negotiate on setting up a tribunal to try Khmer Rouge leaders.

However, critics fear several prominent figures will avoid prosecution because of defection deals struck with Prime Minister Hun Sen.