Cambodia's UN-backed war crimes tribunal officially set June 27 as the start date for a highly-anticipated trial of four top former Khmer Rouge leaders accused of genocide in the 1970s.

The accused are 'Brother Number Two' Nuon Chea, former foreign minister Ieng Sary, his wife and ex-social affairs minister Ieng Thirith, and former head of state Khieu Samphan.

They face charges of war crimes, crimes against humanity, genocide and related crimes under Cambodian law in connection with the deaths of up to two million people from starvation, overwork and execution between 1975 and 1979.

The initial hearing will start on Monday, June 27 and will focus on technical issues and discuss witness and experts lists, the court said in a document posted on its website on Monday.

The trial will be the court's second following the landmark July conviction of former Khmer Rouge prison chief Kaing Guek Eav, known as Duch, who was sentenced to 30 years in jail.