Amnesty International is accusing the United Arab Emirates and allied Yemeni security forces of war crimes for alleged torture in secret prisons throughout southern Yemen.
"The UAE, operating in shadowy conditions in southern Yemen, appears to have created a parallel security structure outside the law, where egregious violations continue to go unchecked," Amnesty's Tirana Hassan said in a new report Wednesday.
"The vacuum of accountability makes it even harder for families to challenge the lawfulness of detention. Even after Yemeni prosecutors have tried to assert their control over some prisons, UAE forces have ignored or severely delayed their release orders on several occasions," she said.
The UAE is a key member of the Saudi-led coalition fighting to drive Iranian-backed Houthi rebels out of Yemen.
Current and former detainees, suspected of terrorism, say UAE soldiers and Yemeni forces operating outside the command of the Yemeni government carried out beatings, electric shocks, and sexually related violence in the secret prisons and at a coalition military base.
One former prisoner says he was forced to stand in a hole and buried up to his head.
Families of detainees say their relatives were arrested arbitrarily and held without charges for as long as two years.
The families say UAE officials give them no information and sometimes responded with threats when the families demanded to know where their relatives are.
The UAE has repeatedly denied running secret prisons. It says Yemeni authorities are in complete control of the country's judiciary and prison system.
Amnesty is calling on the United States to take a stand against the use of torture in Yemen and refuse any information gained through the use of such methods in the fight against terrorism.