Fifteen prisoners at Guantanamo Bay have been released to the United Arab Emirates in the single largest transfer of detainees during the Obama administration.

The release of 12 Yemeni nationals and three Afghans comes amid a renewed push to whittle down the number of detainees held at the U.S. base in Cuba. The men have been cleared for transfer by U.S. government departments and agencies.

The Pentagon says 61 detainees remain at Guantanamo.

President Barack Obama has been seeking to close the detention center amid opposition from Congress.

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