The UN war crimes tribunal on September 16 freed Ieng Thirith, 80, notoriously known as the "First Lady" of Cambodia's murderous Khmer Rouge regime, reasoning she was mentally unfit to stand trial.

Witnesses said Ieng Thirith left the Extraordinary Chambers in the Court of Cambodia (ECCC) detention facility the same day and was taken home in Phnom Penh.

Ieng Thirith is sister-in-law of Khmer Rouge supreme leader Pol Pot and wife of the regime’s foreign minister Ieng Sary.

Used to serve as minister for social affairs under the regime, she was accused of involvement in the deaths of two million Cambodians and has been charged with war crimes, genocide and crimes against humanity.

Three other senior Khmer Rouge leaders are currently on trial for the same charges, including Ieng Thirith’s husband Ieng Sary, Nuon Chea and Khieu Samphan.

Established in 2007, the UN-backed tribunal only completed a single trial on Kaing Guek Eav, alias Duch, who was director of a notorious torture centre in Phnom Penh . Duch was sentenced to life imprisonment.-VNA