Cambodian authorities have arrested two leading figures from the notorious 1970s Khmer Rouge regime and charged them with crimes against humanity.
Ieng Sary has repeatedly denied responsibility for any crimes
Former Foreign Minister Ieng Sary and his wife, Ieng Thirith, were taken into custody in the capital, Phnom Penh.
The pair, who deny any wrongdoing, are due to appear at a UN-backed genocide tribunal on Wednesday.
The brutal Maoist regime, which ruled between 1975 and 1979, is blamed for more than one million deaths.
A tribunal was established last year to bring surviving leaders to the dock.
"Today Ieng Sary and Ieng Thirith have been arrested in execution of an arrest warrant... for crimes against humanity and war crimes as regards Ieng Sary and for crimes against humanity concerning Ieng Thirith," a statement from the tribunal said.
Purge of intellectuals
Police surrounded the couple's Phnom Penh house early in the morning.
WHO WERE THE KHMER ROUGE?
Maoist regime that ruled Cambodia from 1975-1979
Founded and led by Pol Pot, who died in 1998
Abolished religion, schools and currency in a bid to create agrarian utopia
Brutal regime that did not tolerate dissent
More than a million people thought to have died from starvation, overwork or execution
They searched the house for three hours and then drove Ieng Sary and his wife to the tribunal in a convoy of vehicles.
The couple, who have been living freely in the Cambodian capital for more than 10 years, were key members of the Khmer Rouge leadership.
Ieng Sary was Pol Pot's brother-in-law - his wife's sister was married to the Khmer Rouge founder. His wife, Ieng Thirith, was the Khmer Rouge's social affairs minister.
As foreign minister, he was often the only point of contact between Cambodia's rulers and the outside world.
He was responsible for convincing many educated Cambodians who had fled the Khmer Rouge to return to help rebuild the country.
Many were then tortured and executed as part of the purge of intellectuals, some of them diplomats from his own office.
Prosecutors for the tribunal have said there is evidence of Ieng Sary's participation in crimes, including planning, directing and co-ordinating forced labour and unlawful killings.
Ieng Sary has repeatedly denied any crime. In 1996 he became the first senior leader from the Maoist regime to defect and as a result was granted a royal pardon.
But analysts say the validity of that agreement looks set to be tested with his arrest by the court.
Ieng Sary and Ieng Thirith are the third and fourth people to be targeted by the tribunal.
KHMER ROUGE TRIBUNAL
Will try cases of genocide and crimes against humanity
Five judges (three Cambodian) sit in trial court
Cases decided by majority
Maximum penalty is life imprisonment
Budget of $56.3m
In September, Pol Pot's second-in command, 82-year-old Nuon Chea, was charged with war crimes and crimes against humanity.
Two months before that, Kang Kek Ieu - or Duch - the head of the notorious Tuol Sleng prison, was charged with crimes against humanity.
Their trials, before a team of Cambodian and international judges, are expected to start in 2008.
Other top leaders are already dead. Pol Pot died in 1998 and Ta Mok - the regime's military commander and one of his most ruthless henchmen - died in July 2006.