Landmark Khmer Rouge trial starts
Duch ran a Khmer Rouge prison where almost all inmates were killed
The long-awaited UN-backed trial of a former Khmer Rouge leader in Cambodia has opened at a Phnom Penh court, 30 years after the murderous regime fell.
Kaing Guek Eav - better known as Duch - was head of a notorious prison camp and is accused of presiding over the murder and torture of at least 15,000 inmates.
The trial is the result of a decade of painstaking and often ill-tempered negotiations, a BBC correspondent says.
People queued for hours to attend the hearing and see the ex-prison chief.
For the survivors, the opening day of the trial offered the first opportunity to see a leading figure in the Khmer Rouge face justice.
These first days are mainly procedural, with witness testimony expected to be heard only during next month's hearings, the BBC's South East Asia correspondent, Jonathan Head, says.
Duch was driven by bulletproof car from a detention centre to the specially-built court-room.
He is one of five former Khmer Rouge leaders who will face trial and is unusual in that he has expressed regret for what he did, and asked the forgiveness of his victims.
Tribunal spokesman Reach Sambath called it "a very big day for the Cambodian people because the justice that they have been waiting for 30 years is starting to get closer and closer".
"I came here to see the trial with my own eyes, so I could tell villagers who could not be here," Mahd Musa, 54, who lost seven family members during the Khmer Rouge period, told Reuters news agency.
"It is a very important day for me. I cannot miss it."
He is accused of personally overseeing the systematic torture of more than 15,000 prisoners.
Those who survived the ordeal were sent for execution in the so-called "killing fields".
Many of the inmates were loyal party members who were caught up in the frenzy of paranoid killing that accompanied the Khmer Rouge's final months in power, the BBC's South East Asia correspondent says.
A born-again Christian, he is said to have co-operated with investigating judges - and is expected to reveal important information about the decisions made by the organisation's leadership.
His information could help in the trials set for later this year of the five other defendants, analysts say.
They include the surviving top leaders Nuon Chea, Ieng Sary and Khieu Samphan, who are all elderly and in poor health.
If preparations for their trials get bogged down, as seems likely, Comrade Duch may be the only man ever held to account for the Khmer Rouge atrocities, our correspondent adds.
But the man most wanted for crimes against humanity in Cambodia will never be brought to justice.
WHO WERE THE KHMER ROUGE?
Maoist regime that ruled Cambodia from 1975-1979
Founded and led by Pol Pot, who died in 1998
Abolished religion, schools and currency in a bid to create agrarian utopia
Up to two million people thought to have died from starvation, overwork or execution
Pol Pot, the founder and leader of the Khmer Rouge, died in a camp along the border with Thailand in 1998, the same year his few remaining guerrillas agreed to finally abandon their fight.
As many as two million people are thought to have died from starvation, overwork and execution as the Khmer Rouge emptied the cities to send people to work on collective farms during its four years in power.
Cambodia originally asked the United Nations and international community to help set up a tribunal into the genocide more than a decade ago.
A joint tribunal was finally set up in 2006 following long drawn-out negotiations between the Phnom Penh government and the UN.
Bail hearings, appeals and pre-trial procedures have contributed to further delays.