Kaing Guek Eav apologised for his actions under the Khmer Rouge regime
A key Khmer Rouge leader has admitted responsibility for crimes committed during the regime's brutal rule.
Speaking at a UN-backed tribunal in Cambodia, Kaing Guek Eav - also known as Duch - expressed "regretfulness and heartfelt sorrow" for his actions.
Duch is accused of torture, crimes against humanity and premeditated murder for his alleged role in the deaths of more than 10,000 people.
The Khmer Rouge killed two million people in their four years in power.
"May I be permitted to apologise to the survivors of the regime, and also the loved ones of those who died brutally during the regime," Duch told the court.
"I ask not that you forgive me now, but hope you will later."
Prosecutors opened their case against Duch on Tuesday - the second day of this trial - and vowed to get justice for his many victims.
"For 30 years, one-and-a-half million victims of the Khmer Rouge have been demanding justice for their suffering," said co-prosecutor Chea Leang.
"Justice will be done. History demands it."
Guy De Launey, the BBC's correspondent in Phnom Penh
The admission of responsibility was dramatic but it was all part of the plan for Comrade Duch's defence team.
Their client had been co-operating with the investigating judges and had already expressed his remorse to them.
An admission of culpability in a public courtroom broadcast across the country should carry much greater weight for the people of Cambodia.
Duch is the first Khmer Rouge leader to face the tribunal - with four more of the regime's senior figures in custody and awaiting trial.
He ran the Tuol Sleng prison, which, the co-prosecutor said, "formed an integral and indeed vital role in a widespread attack on the population of Cambodia".
Only a few people are known to have survived their time at Tuol Sleng, which is now a genocide museum lined with photographs of the thousands who died there.
"As a member of the [Khmer Rouge] I recognise responsibility for what happened at Tuol Sleng," Duch told the tribunal.
But he also insisted that he did not hold a senior role in the regime, and that he had had little choice but to work there.
"I was in a life and death situation for myself and my family," he said.
Duch is the only defendant who has admitted his part in the atrocities and expressed remorse.
Now a slight, grey-haired 66-year-old, the former prison warder has been polite and studious in taking notes in court.
But the charges against him are grave, and when the prosecutors read out the long indictment against him on Monday, it was full of gruesome details.
It described medieval methods of torture and execution allegedly carried out by Duch when he was in charge of the notorious Tuol Sleng prison.
"Several witnesses said that prisoners were killed using steel clubs, cart axles, and water pipes to hit the base of their necks," the indictment said.
"Prisoners were then kicked into the pits, where their handcuffs were removed. Finally the guards either cut open their bellies or their throats," it said.
Duch's job was to extract confessions from prisoners of counter-revolutionary activity, but "every prisoner who arrived at S-21 [Tuol Sleng] was destined for execution", the document said.
Duch has been in detention since he was discovered in the Cambodian countryside in 1999 by British journalist Nic Dunlop.
Mr Dunlop, who attended Tuesday's hearing, said it was "surreal" to see him in a courtroom.
"I think what's really interesting is to see the description of S-21 being given to Duch, and to see if there is any registration on his face whatsoever," he told reporters.
"As far as I can see there's been absolutely no reaction from him," he said.
The Khmer Rouge took over Cambodia in 1975, ousting a US-backed government shortly after the US pulled out of neighbouring Vietnam.
Driven on by Maoist principles, they attempted to create a peasant society by systematically emptying the cities and forcing the population to work in the fields.
By the time the Vietnamese army invaded and overthrew the Khmer Rouge in 1979, the regime had executed, starved or overworked to death up to two million Cambodians.