PHNOM PENH - A woman who said she survived the Khmer Rouge's main torture centre identified at Cambodia's UN-backed war crimes court Monday chilling photos of family members killed at the jail.

Nam Mon, 48, was testifying at the trial of prison chief Duch, who is accused of overseeing the torture and extermination of around 15,000 people who passed through Tuol Sleng prison during the regime's brutal 1975-1979 rule.

"This is the photo of my father the moment he was dying," Nam Mon said after being shown an image of an emaciated man lying down, staring into the air.

As a court-appointed psychiatrist comforted her, Nam Mon identified black and white prison photos of her parents, three brothers and a sister-in-law executed at the prison.

Recognised as a civil claimant in the case against Duch, Nam Mon told the court Thursday that one of her brothers had been ordered to kill her father.

Her testimony was adjourned last week when she began to weep uncontrollably.

Nam Mon said that her two elder brothers were guards at Tuol Sleng before her family was killed at the notorious jail, while she initially lived and worked there as a medic before being interrogated herself.

"I treated the sick. I saw prisoners who were beaten and interrogated... I only saw the wounds and the bleeding on bodies of prisoners while I treated them," Nam Mon said Monday.

The 66-year-old Duch, real name Kaing Guek Eav, begged for forgiveness from victims near the start of his trial for war crimes and crimes against humanity, after accepting responsibility for his role overseeing the jail.

But he has consistently rejected claims by prosecutors that he held a central leadership role in the Khmer Rouge, and says he never personally executed anyone.

Led by Pol Pot, who died in 1998, the Khmer Rouge emptied Cambodia's cities in a bid to forge a communist utopia. Up to two million people were executed or died of starvation, overwork or torture.

Four other former Khmer Rouge leaders are currently in detention and are expected to face trial next year.