Phnom Penh(AP): The former Khmer Rouge "First Lady" facing trial for crimes against humanity on wednesday lost her appeal for release from Cambodia's UN-backed genocide court in a verdict her lawyer called unfair.

Ieng Thirith, the regime's former social affairs minister, is one of five top cadres in the sights of the UN war crimes tribunal over atrocities committed during the Khmer Rouge's 1975-1979 rule.

The judge told the court that 76-year-old Ieng Thirith needed to stay in jail as "there are well-founded reasons to believe" that she committed the crimes for which she has been charged. "The provisional detention order is still effective," the judge said. "The court rejects the appeal."

After the ruling, Ieng Thirith's lawyer Phat Pouv Seang told reporters the verdict was "unfair" because it didn't take into account his arguments that she should bereleased because of her declining health.

"The court's decision today doesn't give justice to my client. It means there is bias in this case," Phat Pouv Seang said. "My client is elderly and she has been sick a long time and she can't escape anywhere," he added.

The four other defendants at the tribunal are mostly in their 70s and 80s, and worries for their health have also cast a cloud over the proceedings as critics worry they could die before trials are completed. Khmer Rouge leader Pol Pot died in 1998.

It has taken three decades to start bringing senior officials of the Khmer Rouge -- who left up to two million people dead from overwork, starvation, torture or execution -- to trial at the joint Cambodia-UN tribunal.

The court was not established until 2006, and the trials of the regime's five surviving senior leaders are not due to begin until later this year.