Prosecutors at Cambodia's United Nations-backed war crimes tribunal have appealed the court's decision to unconditionally release the aging sister-in-law of former Khmer Rouge leader Pol Pot.

In a statement Friday, the prosecutors said they want tighter restrictions on the release of Ieng Thirith , who a day earlier was found unfit to stand trial for genocide and other charges because of her dementia.

The prosecutors say the conditions are to ensure she does not flee the country or interfere with witnesses. They also expressed concern about her safety and said she should be subject to regular health examinations.

The court says it has delayed the release of the 80-year-old, once dubbed the “First Lady” of the Khmer Rouge, until it decides on the appeal.

Thirith was charged with crimes against humanity, genocide, homicide, torture and religious persecution related to the 1975-1979 rule of the Khmer Rouge. The radical communist rule resulted in the deaths of some 1.7 million Cambodians.

Thursday's decision “postponed indefinitely” the charges against Thirith, but said the ruling is not a reflection on her guilt or innocence. But it also left open the possibility that she could still face charges in the unlikely event that her health improves.

The tribunal is seeking justice for the victims who died of starvation, execution or lack of medical care during the Khmer Rouge's reign.

Ieng Thirith and her three co-defendants are the most senior survivors of the regime's leadership. All defendants deny the charges. Pol Pot died in 1998.