Duch (centre) ran the Tuol Sleng jail, known as a 'killing machine'

The UN-backed court is hearing a bail request from Kang Kek Ieu, or Duch, the former head of a notorious prison.

Duch was the first of five senior Khmer Rouge officials to be arrested and charged by the court.

More than a million people are thought to have died during the four years of Khmer Rouge rule between 1975 and 1979.

Tribunal spokesman Peter Foster described the hearing as a "milestone" for the court, which was set up last year after decades of wrangling.

"It's a big day," he said. "The spotlight will now be on Cambodia."

'Sense of relief'

Duch, who is now in his 60s, was driven to the court from a nearby detention centre, where he has been held since his arrest in July.

WHO WERE THE KHMER ROUGE? Maoist regime that ruled Cambodia from 1975-1979 Founded and led by Pol Pot, (above) who died in 1998 Abolished religion, schools and currency in a bid to create agrarian utopia Brutal regime that did not tolerate dissent More than a million people thought to have died from starvation, overwork or execution

Trial raises hope of justice Brutal Khmer Rouge regime

Three decades ago, he ran Tuol Sleng jail in Phnom Penh, where thousands of people were tortured and executed by the Khmer Rouge regime.

Lawyers for the elderly ex-leader are appealing for bail on the grounds that he was held without charge under the jurisdiction of another court for eight years.

Proceedings inside the small chamber were broadcast to hundreds of people - journalists and ordinary Cambodians - outside in the court's compound.

The BBC's Guy De Launey, in Phnom Penh, says that the former Khmer Rouge jailer is unlikely to be released, but his appearance in court shows the tribunal is finally moving forward.

Co-prosecutor Robert Petit told the BBC the bail hearing would allow the people to see that justice was being done.

"I hope that it will provide Cambodians with a certain sense of relief that the process is ongoing and is transparent, or as transparent as it can be."

Fifty-five year old Chhouek Sao, who lost five family members to the regime, said he wanted justice.

"It's obvious that justice has been delayed and some people are so frustrated by waiting for so long," he told the French news agency AFP.

Five senior Khmer Rouge officials are now in the custody of the tribunal.

On Monday, former head of state Khieu Samphan was formally charged with committing crimes against humanity.

Pol Pot's second-in-command Nuon Chea and the former foreign and social affairs ministers Ieng Sary and Ieng Thirith are also facing charges.

Their trials are expected to begin next year.