Cambodian officials say a former top Khmer Rouge military officer who was expected to be indicted for alleged atrocities has died.

Deputy regional commander Ek Sam Oun said Wednesday that former Khmer Rouge air force chief Sou Met died on June 14 after a long illness. He had been living in northwestern Battambang province and was believed to be 76.

A U.N.-backed tribunal is currently trying two former top leaders of the Khmer Rouge on charges of crimes against humanity and other offenses during the 1970s. The group's radical policies led to the deaths of an estimated 1.7 million people.

Leaked tribunal documents indicated that prosecutors sought to indict Sou Met for allegedly overseeing mass purges. Tribunal spokesman Lars Olsen said he was never officially named a suspect.