Phnom Penh - Cambodia's UN-backed Khmer Rouge tribunal on Friday postponed a hearing of the regime's former head of state after his controversial French lawyer failed to appear at court.

Khieu Samphan, 77, was in court to appeal an extension of his pre-trial detention, but judges adjourned the hearing until April 3 after it was revealed that international co-defence lawyer Jacques Verges was still in France.

Cambodian co-defence lawyer Sa Sovan told the court Verges missed his flight from Paris Thursday because "a person very close to him" had been injured in an accident.

"He wanted to attend but he had to be with a colleague who had a serious accident," Sa Sovan said at a press conference after the hearing. "It is a life or death situation."

Verges previously represented Nazi war criminal Klaus Barbie and the terrorist known as Carlos the Jackal and is said to have befriended Khieu Samphan and other members of the Khmer Rouge while they were studying in Paris in the 1950s.

Khieu Samphan is one of five former Khmer Rouge leaders facing trial for their roles in the deaths of up to 2 million people through execution, starvation or overwork during the ultra-Maoist group's 1975-79 rule.

The first stage of the trial of former Tuol Sleng torture facility chairman Kaing Guek Eav, known by his revolutionary name Duch, was held last week.

The Khmer Rouge tribunal announced on Monday that Duch's trial would resume on March 30.

He is the first detainee to be indicted for crimes against humanity. (dpa)