The surviving leader of Cambodia’s Khmer Rouge is fit to continue his trial for war crimes and genocide, medical experts say, amid fears that the millions of deaths under the ruthless regime may never be brought to justice.

British forensic psychiatrist Seen Fazel says 86-year-old Nuon Chea’s mental health and cognitive function “is currently good”.

“From a physical point of view, I felt he is well enough to continue with the trial,” Professor John Campbell, a geriatrician from New Zealand, told the UN-backed tribunal.

Nuon Chea, Pol Pot’s former deputy, oversaw the “Killing Fields” era in the late 1970s. He is currently on trial alongside former Khmer Rouge head of state Khieu Samphan, who is now 81.

Nuon Chea and Khieu Samphan denied charges including war crimes and genocide from their roles in the brutal regime which killed hundreds of thousands of people in the country’s darkest time in history.

The death of Ieng Sary, the Khmer Rouge’s co-founder, at the age of 87, intensified fears that the remaining former leaders may also die before verdicts can be reached in their trial, reports AFP.