Once a high school in Phnom Penh, the Khmer Rouge converted Tuol Sleng's classrooms into small prison and torture chambers. The prison's former chief, Duch, went on trial before Cambodia's genocide tribunal this week.

Only a few of the estimated 15,000 men, women and children sent to Tuol Sleng are known to have survived under Duch's supervision (1975-79). Most were executed and buried in mass graves at the so-called "Killing Fields".

Tuol Sleng's horrors were screened in the courtroom of the UN-backed tribunal on Wednesday. A black-and-white video showed scenes of the abandoned prison, including several swollen corpses strapped to iron bed frames where they were apparently tortured. It also showed five children who survived by hiding in a pile of washing.

Prosecutors insisted on introducing the film, shot by Vietnamese soldiers after they drove the Khmer Rouge from power in 1979, as evidence against Duch. They say "it is an absolute must for this trial chamber to have all available evidence."

Duch's lawyers were shocked by the prosecution's bid to use the film against their client. They questioned its authenticity, arguing it should be considered a Vietnamese propaganda film.

They also opposed the submission of more than 50 new documents, including interrogation reports with Duch's alleged handwritten notes ordering the individuals to be put to death.

The arguments came as the tribunal wrapped up the opening hearings of Duch's trial, after just a day and a half. The full trial is expected to start next month.

Duch, now aged 66, has taken responsibility for his rule at Tuol Sleng and has expressed regret for his crimes. The prison is now a museum documenting Cambodia's genocide.

More about Cambodia's tribunal: FAQ: Cambodia's first 'Killing Fields' trial

Related articles:

    * First trial of senior Khmer Rouge leader opens
    * Cambodia's genocide trial starts against Duch
    * Lawyers feel intimidated by Cambodia tribunal
    * Three decades of impunity in Cambodia
    * Cambodia: Legal Justice Lessens Anger of Villagers
    * Cambodia genocide trial delayed
    * USpledges US$1.8 million for Cambodia tribunal
    * Quarrel over temple rekindled
    * Khmer Rouge camp chief indicted
    * Khmer Rouge tribunal calls for more funds
    * Controversy at the Cambodia tribunal
    * Last Khmer Rouge leader arrested
    * Cambodia - starting from scratch
    * Confessing the killing fields
    * Dutch documentary premieres in Phnom Penh
    * Khmer Rouge General Arrested
    * UN Leaves Killing Fields
    * The Hidden Legacy of War in Cambodia (Part 2)