A court on Thursday found the two most senior surviving leaders of the Khmer Rouge regime, which brutalized Cambodia during the 1970s, guilty of crimes against humanity and sentenced them to life in prison.

The chief judge, Nil Nonn, said the court found that there had been “a widespread and systematic attack against the civilian population of Cambodia” and that the two former leaders were part of a “joint criminal enterprise” that bore responsibility. They were convicted of murder and extermination, among other crimes.

More than 1.7 million people died under Khmer Rouge rule between 1975 and 1979.