The re-trial of a former Khmer Rouge commander for his alleged role in the murder of three backpackers in 1994 has begun in Cambodia.

The appeal court is going ahead with the trial of Chhouk Rin, despite his refusal to attend the hearing, which he argues is politically motivated.

The court ordered Chhouk Rin to appear in court on 4 September, when a verdict is due to be handed down.

Chhouk Rin had been convicted two years ago of the murders, but he was set free shortly afterwards when another court ruled he was covered by an amnesty for guerrillas who laid down their arms.

Correspondents say pressure from the tourists' families and governments has forced the Cambodian authorities to hear the case, seen by many as a litmus test for the government's commitment to try former Khmer Rouge leaders, again.

Victim's father in court

Chhouk Rin's lawyer said on Tuesday that the court had refused to allow the defence sufficient time to summon witnesses, so the defendant was refusing to attend as he felt he would not get a fair hearing.

Australian David Wilson, one of those killed

The British and Australian ambassadors were both in court, alongside the father of the French victim of the 1994 attack and his lawyer.

Australian David Wilson, Frenchman Jean-Michel Braquet and Briton Mark Slater were kidnapped in an ambush of a train by former Khmer Rouge rebels.

At least 10 Cambodians were killed during the attack.

The three foreigners and several Cambodians were taken to the nearby Vine Mountain rebel base in the southern Cambodian province of Kampot.

They were killed after negotiations for their release and the payment of a $150,000 ransom broke down.

International concern

The Khmer Rouge commander of Vine Mountain, Nuon Paet, was jailed for life in June 1999 for his role in the affair.

His superior officer and the man he said had ordered the tourists killed, Sam Bith, was arrested in May and is in jail awaiting trial.

But there is continuing international concern that Cambodia's government is not serious about its commitment to bring former Khmer Rouge leaders to trial.

Negotiations between the UN and the Cambodian Government to set up an international tribunal broke down in February, after UN officials said they were concerned the planned hearings would not meet international standards of justice.

But last week Cambodia's Prime Minister Hun Sen agreed to work with the UN to revive talks on the issue.