Ieng Thirith, former minister of social affairs for the Democratic Kampuchea, known as Khmer Rouge, who was found mentally unfit to stand trial in 2012, died on Saturday at the age of 83, according to a statement of the Extraordinary Chambers in the Courts of Cambodia (ECCC).

"The ECCC has been informed by the legal guardian that the accused person Ieng Thirith passed away at approximately 10:30 a.m. on August 22, 2015 in Pailin province, Cambodia," the statement said.

In September 2010, Ieng Thirith was indicted on charges of genocide, crimes against humanity and grave breaches of the Geneva Conventions of 1949, it said, adding that the proceedings against her were stayed in 2012 after she had been found unfit to stand trial due to progressive dementia, and she was released under a regime of judicial supervision.

Ieng Thirith was one of four original Khmer Rouge leaders arrested and expected to face trial for atrocity crimes at the United Nations-backed ECCC.

Her husband, Ieng Sary, the former foreign minister of the regime, died in the ECCC's custody in March 2013 at the age of 87.

The remaining two leaders of the regime, Nuon Chea, 88, the chief ideologue of the Communist Party of Kampuchea during the regime, and Khieu Samphan, 84, the regime's former head of state, were found guilty of crimes against humanity and sentenced to life in prison in August last year.

Currently, the duo are facing another trial for genocide charges.

Established in 2005, the ECCC is seeking justice for the victims who died of starvation, exhaustion, lack of medical care or execution during the regime from 1975 to 1979.