PHNOM PENH - The Khmer Rouge prison chief was to give his concluding remarks on Wednesday in final arguments at Cambodia's war crimes court, nearing justice for the "Killing Fields" atrocities three decades ago.

Kaing Guek Eav - better known as Duch - has repeatedly used his trial to apologise for his role in the horrors of the late 1970s hardline communist regime, which killed up to two million people.

"Duch is expected to speak and what we're told is he's expected to speak one or two hours," said court spokesman Lars Olsen.

The prosecution, which will make its own final remarks Wednesday before Duch addresses the court, has indicated it will call on judges to hand him a lengthy sentence.

For Cambodians, the controversial tribunal, established in 2006 after nearly a decade of negotiations between Cambodia and the United Nations, is the last chance to find justice for the Khmer Rouge's crimes during its 1975-1979 rule.

Since his trial began in February, Duch, 67, has publicly asked for forgiveness for overseeing the murders of around 15,000 men, women and children at Tuol Sleng prison, built in a former high school.

He is charged with crimes against humanity, war crimes, torture and premeditated murder, and faces a maximum term of life in prison by the tribunal, which does not have the power to impose the death penalty.

Duch is expected to apologise again Wednesday as his defence bids to lessen his sentence, however prosecution and civil party lawyers have this week rejected his accounts of the past and called for a harsher decision.

After final arguments conclude this week, the verdict is expected early next year.

Hundreds of Cambodians are set to attend the specially built courtroom on the outskirts of Phnom Penh for the hearing on Wednesday, which is due to start at 9:00 am (0200 GMT).

Duch will sit with judges, lawyers and witnesses behind a massive bulletproof screen to prevent possible revenge attacks.

This week's proceedings are being broadcast live by all Cambodian television stations, court officials said.

Tuol Sleng prison was at the heart of the Khmer Rouge security apparatus and thousands of inmates were taken from there during Duch's tenure for execution at nearby Choeung Ek, an orchard now known as the "Killing Fields."

Led by "Brother Number One" Pol Pot, the Khmer Rouge was responsible for one of the worst horrors of the 20th century, wiping out nearly a quarter of the population through starvation, overwork and execution.

Rising to power as a tragic spin-off of the US conflict in Vietnam, the movement emptied Cambodia's cities to take society back to a rural "Year Zero," purging city dwellers, intellectuals and even people who wore glasses.

The Khmer Rouge was ousted by Vietnamese-backed forces in 1979, but continued to fight a civil war until 1998. Pol Pot died in the same year.

Duch has been detained since 1999, when he was found working as a Christian aid worker in the jungle, and was formally arrested by the tribunal in July 2007.

The court has faced controversy over allegations of interference by the government and claims that Cambodian staff paid kickbacks for their jobs.

The joint trial of four other more senior Khmer Rouge leaders is expected to start in 2011.

The court is also investigating whether to open more cases against five other former Khmer Rouge cadres after a dispute between the international and Cambodian co-prosecutors over whether to pursue more suspects.