The United Nations-backed war crimes tribunal in Cambodia has ordered the Khmer Rouge's main jailer to spend the rest of his life in prison for crimes it says were “among the worst in recorded human history.”

The ruling extends a lower court's 19-year sentence that has been appealed by prosecutors as too lenient.

The president of the court chamber, Kong Srim, said in reading the verdict that Kaing Guek Eav, better known as Duch, was a “shocking and heinous” character who deserves the “highest penalty available.”

The tribunal said Duch oversaw a “factory of death” in the 1970s at the feared Tuol Sleng Prison, where an estimated 14,000 people died.

Duch admitted his role in the crimes. But he asked for forgiveness, saying he had only followed strict orders given by senior Khmer Rouge figures.

The 69-year-old Duch responded with little emotion as the verdict was read. But many survivors, including 53-year old Cheam Socheong, said they were satisfied with the sentence.

“After listening to today's verdict, I feel happy and excited to see Duch receiving life imprisonment because he deserves this.”

U.S. Ambassador-at-large for war crimes, Stephen Rapp, aslo welcomed the court's decision.

“I think it is a great day that this first and so important case is concluded, and I think that this is an

important step to justice for the reconciliation for the people of Cambodia.''

Britain's Foreign Office Minister Jeremy Browne welcomed the court's decision in a statement, calling it an “excellent outcome” that closes the darkest chapter in Cambodia's history. He thanked the judges for seeing that justice was done for the vicitms of the Khmer Rouge and their families.

Duch's original 35-year sentence had been reduced to 19 years for time already served in detention. That ruling outraged survivors by raising the possibility that Duch could one day walk free.

Hundreds of Cambodians packed the courtroom in Phnom Penh to witness the historic ruling.

The tribunal is currently trying three other senior Khmer Rouge leaders for crimes against humanity and genocide, among other charges.

It is seeking justice for the estimated 1.7 million people who died from torture, starvation, exhaustion or lack of medical care during the communist regime's rule from 1975-1979.