CAMBODIA'S war crimes court Monday rejected an appeal by former Khmer Rouge social affairs minister Ieng Thirith against her pretrial detention, with presiding Judge Prak Kimsan saying that her continued imprisonment was "still a necessary measure".

He warned that, if freed, the regime's "first lady" could try to pressure victims and witnesses, or fail to show up at court hearings.

Ieng Thirith did not appear at Monday's hearing because she had a headache and was unable to get out of bed, her lawyer said.

The 77-year-old was arrested in 2007 and is charged with crimes against humanity.