A United Nations-backed war crimes tribunal in Cambodia sentenced two top Khmer Rouge leaders to life in jail after finding them guilty of crimes against humanity, a BBC report said.

Nuon Chea, the regime's second in command under despot Pol Pot, and Khieu Samphan, former president of the ultra-Maoist regime, were found guilty of murders and executions carried out under their rule. This is reportedly the first time that top leaders of the Khmer Rouge have been held accountable for their crimes.

Under the Khmer Rouge, between 1975 and 1979, over 2 million people are believed to have been killed from mass executions, starvation and overwork, as the regime tried to create a radical form of agricultural communism. The regime emptied its cities and forced the urban population into working in rural co-operatives, leading to the economy's collapse.

The regime also executed all those it regarded as its enemies, specifically targeting intellectuals, minorities, former officials and their families. Nuon Chea is believed to have driven the regime's ideology while Khieu Samphan was its public face.

For three years, the court has heard testimonies from people who lost entire families to the regime's brutality while prosecutors argued that the two leaders created and enforced policies that killed millions. Both former leaders denied the accusations and expressed remorse but claimed they were not guilty of ordering the deaths or having been aware of them. 

"My anger remains in my heart,'' Suon Mom, 75, whose husband and four children died of starvation, reportedly said, adding: "I still remember the day I left Phnom Penh, walking along the road without having any food or water to drink."

The two former leaders also face a separate genocide trail with the cases being split to speed up judicial proceedings because of the age of the accused. Ieng Sary, former foreign minister, died in March 2013 while his wife, Ieng Thirith, former social affairs minister, was deemed unfit to stand trial.

The only other senior Khmer Rouge leader who was held accountable for the regime's crimes was former prison chief Duch, who was jailed in 2010 for torturing and killing thousands of people branded as the regime's enemies, in Tuol Sleng prison.