The human rights organisation said interviews with Salah Nasser Salim 'Ali, 27, and Muhammad Faraj Ahmed Bashmilah, 37, indicated they were victims of "the US administration's policy of secret detentions around the world."

"Their testimony will hopefully shed light on US detention centres just as sinister, yet less well-known, than Guantanamo," said William Schulz, executive director of Amnesty International USA.

Yemeni authorities said the men had been transferred from the US detention facility at Guantanamo Bay in Cuba about three months ago at the request of US officials, but Amnesty said separate interviews with the Yemeni detainees painted a different picture.

Amnesty said the men could not have been held at Guantanamo based on the length of travel they said they took from their initial confinement in Jordan and their description of underground detention facilities.

Human rights groups have railed against a practice known as rendition, in which detainees are transferred from one country to another, often in secret and without legal safeguards.

"The Department of Defence does not engage in renditions," said Air Force Maj. Mike Shavers, a spokesman for the department that operates the facility at Guantanamo Bay.

Shavers said records of who had been held in Guantanamo were confidential.