In an interview with the Hong Kong-based Far Eastern Economic Review, due to be published on Friday, Kang Kek Leu admitted to being the man formerly known as "Duch", the director of the Security Prison 21 (S21) detention centre in Phnom Penh.

The former prison chief disappeared 20-years ago, when he followed the Khmer Rouge leadership into Cambodia's jungles after the toppling of the murderous regime by a Vietnamese invasion force.

Torture centre

S21, formerly Tuol Sleng High School, was transformed by the Khmer Rouge into a centre for the interrogation and execution of anyone they suspected of opposing their rule.

Prison regulation 6 states no crying whilst receiving lashes or electrocution

More than 12,000 people, including women, children and a number of foreigners, are thought to have passed through the centre's gates during the Khmer Rouge's four years in power - only seven are believed to have survived.

Hundreds of thousands of other Cambodians died in the so-called "killing fields" around the country.

Kang Kek Leu was quoted by the Review as saying that he was deeply sorry for the killings and was willing to face an international tribunal.

But he is also reported to have said that all the executions were carried out on the orders of the top Khmer Rouge leadership.

Spent force

Now, the Khmer Rouge is thought to be a spent force with most of the movement's surviving leadership having surrendered to the government.

Tuol Sleng survivor Vann Nath looks at a picture of his former tormentor

The Khmer Rouge's "Brother Number One", Pol Pot, who led the group during their time in power, died last April.

The BBC's Phnom Penh Correspondent, Caroline Gluck, says the discovery of Duch's whereabouts is likely to strengthen moves to bring those surviving Khmer Rouge leaders to justice.

S21 itself is now a museum, dedicated to those who lost their lives within its walls. Most of those walls have been covered with thousands of pictures of victims, taken by Khmer Rouge officers as part of their methodical record keeping.

The head of the documentation centre of Cambodia, Youk Chang, who has been collecting archival material on the Khmer Rouge, says there is plenty of evidence to prosecute Duch for his part in the killings.