Ieng Thirith was the most powerful woman in the Khmer Rouge
The Khmer Rouge's former social welfare minister has been refused bail by Cambodia's UN-backed genocide court.
Ieng Thirith, 76, is accused of crimes against humanity for her part in the Maoist regime's brutal four-year rule in the late 1970s.
Judges are still considering a bail appeal by her husband, Ieng Sary, who was the regime's foreign minister.
The other three former Khmer Rouge leaders held by the court have already had their requests for bail denied.
Ieng Thirith was one of the Khmer Rouge's founding members and its most powerful woman.
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
Up to two million people thought to have died from starvation, overwork or execution
Her sister was married to the movement's leader, Pol Pot.
Prosecutors say she knew that tens of thousands of people were dying from starvation and disease on brutal collective farms - but did nothing to stop the disaster.
Ieng Thirith denies any wrongdoing. In court her lawyer argued that she required regular treatment for both mental and physical ailments.
But the judges ruled that "detention remains a necessary measure" for Ieng Thirith.
The trials are expected to begin later in the year.
The Khmer Rouge ruled Cambodia from 1975 to 1979. During this period an estimated 1.7 million people died from starvation or overwork as leaders tried to create a classless agrarian society.
Hundreds of thousands of the educated middle classes were tortured and executed.