Duch, former chief of S-21 prison, talks to his laywer, Fracois Roux, on Tuesday. (AP Photo)

The chief of a prison where some 16,000 men, women and children were tortured before being killed appeared on Tuesday before Cambodia'sgenocide tribunal in its first trial over the Khmer Rouge reign of terror more than three decades ago. Kaing Guek Eav - better known as Duch - is charged with crimes against humanity and is the first of five defendants scheduled for long-delayed trials by the UN-assisted court. The two-to-three day hearing which started on Tuesday was procedural, and testimony was expected to begin only in late March.

Duch, driven to and from the hearing in a bullet-proof vehicle from a nearby detention centre, intently followed the proceedings in a courtroom packed with some 500 people. Some of the spectators had filed civil suits against him; others were simply eager to witness the historic event. Millions more Cambodians watched the event live on television.

Duch, 66, is accused of committing or abetting a range of crimes including murder, torture and rape at S-21 prison - formerly a school - where up to 16,000 men, women and children were held and tortured, before being put to death.

Duch, who headed the S-21 prison in Phnom Penh for the Khmer Rouge, is the only defendant to have expressed remorse for his actions, and on Tuesday he again voiced regret for what he did and sought forgiveness. His defence lawyer Francoioux said on Tuesday that his client has been in detention for nine years, nine months and seven days, and called the situation unacceptable.

Francois Roux, defense lawyer:"Duch wishes to ask the victims and the Cambodian population for forgiveness. As he (Duch) said before 'I asked for forgiveness, however I do not ask you to forgive me today but to leave the door open (for it happen) maybe one day."

When the communist Khmer Rouge came to power in 1975 after five years of bitter civil war, many of their countrymen thought peace was at hand. But in their effort to remake society, they instituted a brutal reign of terror that lasted nearly four years, until ended by an invasion by neighbouring Vietnam.

Many victims feared that all the Khmer Rouge leaders would die before facing justice, and getting even one of them on trial is seen as a breakthrough. But there are concerns that the process is being politically manipulated and that thousands of killers will escape unpunished.

The tribunal has been plagued by political interference from the Cambodian government, allegations of bias and corruption, lack of funding and bickering between Cambodian and international lawyers.

Some observers believe Prime Minister Hun Sen, a former Khmer Rouge officer himself, is controlling the tribunal's scope by directing the decisions of the Cambodian prosecutors and judges. However, Prosecutor Robert Petit said Tuesday's hearing was a very significant for Cambodia.

Robert Petit, prosecutor: "I just want to say that this is, I think, a very important day, a very significant day for Cambodia and for the world. And as I said in French, I think, today proceedings, the way they were conducted the way they were conducted bodes well for the commitment of the trial chamber and all the parties to seek justice for the victims of the Khmer Rouge."

The Cambodian side in the tribunal has recently turned down recommendations from the international co-prosecutor to try other Khmer Rouge leaders, as many as six according to some reports. This has sparked criticism from human rights groups.

The S-21 prison is now open to the public and is a popular destination for tourists seeking to uncover more about the crimes committed by the Khmer Rouge regime. The trial comes 30 years after the fall of the Khmer Rouge, 13 years after the tribunal was first proposed and nearly three years after the court was inaugurated.

Others facing trial are Khieu Samphan, the group's former head of state; Ieng Sary, its foreign minister; his wife Ieng Thirith, who was minister for social affairs; and Nuon Chea, the movement's chief ideologue. All four have denied committing crimes.

Information for this report was provided by APTN.