A Cambodian court has convened to deliver its verdict on an appeal by the two most senior surviving members of the Khmer Rouge regime who were sentenced in 2014 to life imprisonment for crimes against humanity.

The two are Khieu Samphan, the 85-year-old Khmer Rouge head of state, and Nuon Chea, the 90-year-old right hand man to the communist group's leader Pol Pot. Both appeared before the Supreme Court Chamber of the U.N.-assisted Khmer Rouge tribunal on Wednesday, and sat impassively before the hearing.

Their lawyers filed lengthy appeals against their 2014 verdicts, alleging a slew of legal and factual errors as well as biases by the judges.

About 1.7 million people are estimated to have died from starvation, disease and executions during the 1975-79 Khmer Rouge rule.