Nuon Chea, the former chief ideologist of the Democratic Kampuchea, or the Khmer Rouge, died on Sunday at the age of 93, according to a spokesperson for the Cambodian tribunal where he was convicted of genocide and crimes against humanity.

"We can confirm that defendant Nuon Chea, 93, passed away this evening on 4 August 2019 at the Khmer-Soviet Friendship Hospital," Neth Pheaktra, a spokesperson for the Extraordinary Chambers in the Courts of Cambodia (ECCC), commonly known as the United Nations-backed Khmer Rouge tribunal, told Xinhua.

The cause of his death was not given, but he had been transferred from the ECCC's detention center to the Khmer-Soviet Friendship Hospital for medical treatment on July 2.

Nuon Chea's wife Ly Kim Seng told AFP that she was by his side until the "last breath," and that his body would be taken to Cambodia's Pailin province for the funeral.

Chea was arrested in 2007 and put on trial before the ECCC on charges of genocide, crimes against humanity and grave breaches of the 1949 Geneva Conventions.

The UN-backed court sentenced him to life in prison last year after he was found guilty of genocide against the ethnic Vietnamese and Cham Muslim minority group.

His lawyers had informed the court that Nuon Chea would appeal, but prosecutors are now expected to ask the Supreme Court chamber to terminate his case following his death, according to a court official.

(With input from Xinhua and AFP)