A UN-backed war crimes tribunal sentenced the former Khmer Rouge chief jailer Monday to 35 years in prison — the first verdict involving a leader of the genocidal regime that destroyed a generation of Cambodia's people.

Kaing Guek Eav, seen in November 2009, was the former head of a notorious Khmer Rouge prison and ordered the torture and killing of thousands of Cambodians in the late 1970s. A UN-backed court found him guilty Monday of war crimes. (Extraordinary Chambers in the Courts of Cambodia/Associated Press)Kaing Guek Eav, also known as Duch, listened impassively as the chief judge read out the verdict, convicting him of crimes against humanity and war crimes. He will serve only 19 years of the sentence because Judge Nil Nonn said the court shaved off the 11 years he has already spent in detention and five more for being illegally detained in a military court.

He had faced a maximum sentence of death, and many victims and their relatives watching the verdict were angry that his sentence was not more severe. Some of them broke down in tears.

Duch, 67, ran the notorious Toul Sleng detention centre reserved for "enemies" of the state. He admitted overseeing the deaths of up to 16,000 men, women and children who passed through its gates and he asked for forgiveness during his 77-day trial.

An estimated 1.7 million Cambodians died from starvation, medical neglect, slave-like working conditions and execution under the Maoist regime that sought to turn the country into an agrarian utopia. Their bodies were dumped in shallow mass graves that still dot the countryside.

The group's top leader, Pol Pot, died in 1998 and four other top members of the Khmer Rouge are awaiting trial.

Unlike the other defendants, Duch was not among the ruling clique and is the only major figure of the regime to have expressed remorse, even offering at one point to face a public stoning.

His surprise request on the final day to be acquitted and freed, however, left many wondering if his contrition was sincere.

Prosecutors asked that he face 40 years in prison.