PHNOM PENH — Two top leaders of Cambodia’s Khmer Rouge regime were found guilty of genocide on Friday, in a landmark ruling almost 40 years after the fall of a brutal regime that presided over the  deaths of a quarter of the population.

The Khmer Rouge’s former head of state Khieu Samphan, 87, and "Brother Number 2" Nuon Chea, 92, are the two most senior living members of the group that seized control of Cambodia from 1975-1979.

The reign of terror led by "Brother Number 1" Pol Pot left some two million Cambodians dead from overwork, starvation and mass executions but Friday’s ruling was the first to acknowledge a genocide.

The defendants were previously handed life sentences in 2014 over the violent and forced evacuation of Phnom Penh in April 1975.

But the judgement at the Extraordinary Chambers in the Courts of Cambodia (ECCC) also found Nuon Chea guilty of genocide against the ethnic Vietnamese and Cham Muslim minority group, among a litany of other crimes.

"The chamber finds that Nuon Chea exercised ultimate decision-making power with Pol Pot and... therefore finds Nuon Chea is responsible as a superior for all the crimes," presiding judge Nil Nonn said.

"This includes the crime of genocide by killing members of Cham ethnic and religious group."

Khieu Samphan was also found guilty of genocide against ethnic Vietnamese, though not against the Cham, he added.

Both parties were sentenced to "life in prison", merging the two sentences into a single term, Nil Nonn said.

Hundreds of people, including dozens of Cham Muslims and Buddhist monks, were bussed to the tribunal located in the outskirts of Phnom Penh to attend the hearing.

Cambodia’s ’Nuremberg’

The events covered by the verdict span the four years of the Pol Pot regime and include extensive crimes against humanity.

"The verdict is essentially the Nuremberg judgement for the ECCC and thus carries very significant weight for Cambodia, international criminal justice, and the annals of history," said David Scheffer, who served as the UN secretary general’s special expert on the Khmer Rouge trials from 2012 until last month.

The revolutionaries who tried to recreate Buddhist-majority Cambodia in line with their vision of an agrarian Marxist utopia attempted to abolish class and religious distinctions by force.

The verdict read out by Nil Nonn presented a society where minorities were targeted and killed, Buddhist monks forcibly defrocked and groups of people executed, while men and women were coerced into marriages and forced to have sex to produce children for the regime.

The atrocities fell under the additional list of charges, which the two men were found guilty of as well.

Los Sat, a 72-year-old Cham Muslim man who attended the verdict hearing with his wife, said he had lost "too many" family members under the regime.

"I am really satisfied with the sentences," he said, beaming as he left the court. "They brought suffering to my relatives."

Youk Chhang, head of the Documentation Center of Cambodia -- a research organisation that provided the court with evidence -- said the verdict will "affirm the collective humanity of the victims and give recognition to the horrible suffering".

"It can provide a sense of closure to a horrible chapter in Cambodian history," he said.

The hybrid court, which uses a mix of Cambodian and international law, was created with UN backing in 2006 to try senior Khmer Rouge leaders.

Only three people have been convicted by the court, costing more than $300 million.

Former Khmer Rouge foreign minister Ieng Sary and his wife died without facing justice, while Pol Pot passed away in 1998.

The number of allegations against Nuon Chea and Khieu Samphan was so vast the court split the trials into a series of smaller hearings in 2011. — AFP