Nuon Chea and Khieu Samphan were part of regime responsible for the deaths of up to two million Cambodians.

Cambodia’s UN-backed court upheld life sentences for two top former Khmer Rouge leaders for crimes against humanity, a verdict welcomed by survivors of the brutal regime.

“Brother Number Two” Nuon Chea, 90, and ex-head of state Khieu Samphan, 85, were the first top leaders to be jailed in 2014, belonging to a regime responsible for the deaths of up to two million Cambodians from 1975 to 1979.

The duo appealed their convictions, accusing the court of a string of errors and the judges of failing to remain impartial due to their personal experiences under the regime.

But in a lengthy ruling on Wednesday, after months of hearings, the bench upheld the bulk of the convictions and the jail terms, but accepted some legal errors had been made in the initial trial.

Most of the victims of the Khmer Rouge “Killing Fields” regime died of starvation, torture, exhaustion or disease in labour camps or were bludgeoned to death during mass executions.

A fifth of the population was killed.

READ MORE: Key facts on the Khmer Rouge

The UN-backed Supreme Court Chamber convicted Chea and Samphan of crimes against humanity, murder, persecution on political grounds and other inhumane acts over the forced evacuation of the capital, Phnom Penh, after the fall of the city in 1975.

“The Supreme Court Chamber affirms the sentence of life imprisonment imposed by the trial chamber on both Nuon Chea and Khieu Samphan,” judge Kong Srim said.

“The Supreme Court orders that Nuon Chea and Khieu Samphan remain in custody.”

Nuon Chea and Khieu Samphan sat impassively as the decision was read out.

“I am so happy with the convictions,” Chhun Leap, 74, who lost around 50 relatives during the Khmer Rouge years, told AFP news agency after leaving the courtroom.

“They are monsters and this is their fate.”

Message for the leaders

David Scheffer, the UN Secretary-General’s envoy to the tribunal, said that the judgment sent a message to leaders around the world.

“What happened today in this courtroom ultimately can reach your domain,” Scheffer told reporters at the court.

“I will just say that, perhaps the leadership of North Korea should take particular note of what occurred here today,” Scheffer said. “International justice isn’t backing down, it is actually forging ahead.”

The Cambodian government also welcomed the court judgment.

“We express our hope that this trial and today’s delivery of the final judgment brings some relief for your pain and suffering,” Deputy Prime Minister Sok An said, addressing survivors of the Khmer Rouge regime.