A Russian who spent 15 years at the U.S. military prison in Guantanamo and was released to the United Arab Emirates for resettlement now faces forced repatriation to his homeland and possible torture, U.N. human rights experts said on Friday.

The United Arab Emirates foreign ministry declined to comment on the case and the U.N. experts' appeal to halt the "imminent" repatriation. The Dubai government's media office did not respond to a request for comment.

Ravil Mingazov, a Muslim Tartar, has been held unlawfully at an undisclosed location in the UAE since being transferred in January of 2017 from Guantanamo where he had been detained without trial or charge, the independent U.N. experts said.

A Russian army veteran, Mingazov was captured in Pakistan in 2002. The offshore prison was opened by former U.S. President George W. Bush to hold terrorism suspects rounded up overseas after the Sept. 11, 2001 attacks.

"We are seriously concerned that instead of releasing him in accordance with the alleged resettlement agreement between the US and the UAE, Mr. Mingazov has been subjected to continuous arbitrary detention at an undisclosed location in the UAE, which amounts to enforced disappearance,” the independent experts said in a joint statement.

"Now, he risks being forcibly repatriated to Russia despite the reported risk of torture and arbitrary detention based on his religious beliefs," said the U.N. human rights experts.

Mingazov had fled Russia over fears of religious persecution, they said.

Any repatriation that fails to respect procedural guarantees, including an assessment of the risks faced by an individual sent back, would violate an absolute international ban on forced return, they said.

The UAE has previously forcibly returned three of 23 former Guantanamo detainees resettled there, without judicial oversight or possibility of appeal, they said.