Ieng Sary's arrest had been widely anticipated as one of five suspects earlier listed by tribunal prosecutors.
Two other Khmer Rouge leaders had already been arrested and charged: Nuon Chea, the former Khmer Rouge ideologist, and Kaing Khek Lev, better known as Duch, the former head of the notorious S-21 or Tuol Sleng prison.
According to prosecutors' papers, the fifth suspect they seek to charge is Khieu Samphan, who was the nominal head of state during the Khmer Rouge rule.
An estimated two million Cambodians died of hunger, disease, overwork and execution during the Khmer Rouge's four years in power in the 1970s.
Like other surviving Khmer Rouge leaders, the 77-year-old Ieng Sary who served as deputy prime minister as well as foreign minister, has repeatedly denied responsibility for any crimes.
However, according to a July 18 filing by the prosecutors to the tribunal's judges, Ieng Sary, "promoted, instigated, facilitated, encouraged and/or condoned the perpetration of the crimes" when the Khmer Rouge held power.
It said there was evidence of Ieng Sary's participation in planning, directing and co-ordinating the Khmer Rouge "policies of forcible transfer, forced labour and unlawful killings".
When the Khmer Rouge lost power in 1979, Ieng Sary retreated with them to the jungles, from where they conducted a guerrilla war.
|Ieng Sary and Ieng Thirith were held overnight |
pending further questioning [AFP]
In 1996, with the group's forces in sharp decline, he defected with a large coterie of followers, setting the stage for the total collapse of the Khmer Rouge two years later.
His belated turn of heart earned him a limited amnesty from then-King Norodom Sihanouk, but one that officials have declared does not apply to the tribunal's charges.
His 75-year-old wife, Ieng Tarith, participated in "planning, direction, co-ordination and ordering of widespread purges ... and unlawful killing or murder of staff members from within the ministry of social affairs", the prosecutors' filing said.