PORT-AU-PRINCE: Fifteen prisoners at the Guantanamo Bay detention center were sent to the United Arab Emirates in the single largest release of detainees during the Obama administration, the Pentagon announced Monday.

The transfer of 12 Yemeni nationals and three Afghans to the UAE comes amid a renewed push to whittle down the number of detainees held at the US prison in Cuba that President Barack Obama aims to close.

The Pentagon says 61 detainees now remain at Guantanamo, which was opened in January 2002 to hold foreign fighters suspected of links to the Taliban or the al-Qaida terrorist organisation. During the Bush administration, 532 prisoners were released from Guantanamo, often in large groups to Afghanistan and Saudi Arabia.

The latest batch of released prisoners had been held without charge at Guantanamo, some for over 14 years. They were cleared for release by the Periodic Review Board, comprised of representatives from six US government agencies.

The UAE successfully resettled five detainees transferred there last year, according to the Pentagon.

Lee Wolosky, the State Department's special envoy for Guantanamo's closure, said the U.S. was grateful to the United Arab Emirates for accepting the latest group of 15 men and helping pave the way for the detention center's closure.

"The continued operation of the detention facility weakens our national security by draining resources, damaging our relationships with key allies and partners, and emboldening violent extremists," Wolosky said.

In the United Arab Emirates, the state-run WAM news agency had no reports on the Guantanamo transfers on Tuesday and UAE officials declined to immediately comment on the Pentagon announcement.

Obama has been seeking to close the detention center amid opposition from Congress, which has prohibited transferring detainees to the U.S. for any reason. The administration has been working with other countries to resettle detainees who have been cleared for transfer.

Naureen Shah, Amnesty International USA's director of national security and human rights, said the transfers announced Monday are a "powerful sign that President Obama is serious about closing Guantanamo before he leaves office."

US Representative Ed Royce, a Republican from California who is chairman of the House Foreign Affairs Committee, criticized the Obama administration for recent releases, portraying the freed detainees as "hardened terrorists."

The Office of the Director of National Intelligence says 5 percent of Guantanamo prisoners released since Obama took office have re-engaged in militant activities and an additional 8 percent are suspected of doing so. That compares with 21 percent confirmed and 14 percent