The Obama administration is facing renewed accusations from Republican lawmakers of putting national security at risk following the release of 15 more Guantanamo Bay detainees -- including former Usama bin Laden bodyguards and Al Qaeda bomb experts -- as the Pentagon works to fulfill the president’s vow to shutter the camp by the end of his term. 

“It is reckless for the administration to continue to release terrorists like these to fulfill a misguided campaign promise to empty and close Guantanamo," Sen. Kelly Ayotte, R-N.H., said in a statement on Tuesday.

The newly announced transfer of 15 detainees – 12 Yemenis and three Afghans – to the United Arab Emirates marks the single largest release under the Obama administration.

With five months remaining in President Obama’s term, the transfer is the latest effort to shrink the prison camp’s population as part of the president’s goal to shutter the facility.

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."

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

But the transfers, especially of the remaining detainees, also come with substantial risk, GOP lawmakers warn.

“It is unconscionable that this administration continues to release known terrorists. Several terrorists released by the Obama administration have returned to the battlefield and re-engaged in attacks against coalition forces and our allies,” Senate Intelligence Committee Chairman Richard Burr, R-N.C., said in a statement. “The administration continues to put our national security at risk in misguided attempts to fulfill campaign pledges and to cement the President’s legacy.” 

Ayotte recently released unclassified files on some of the remaining detainees, and said Tuesday that the latest batch of 15 are “among the worst terrorists.”

"The terrorists this administration just released include individuals who fought on the frontlines against U.S. and other coalition forces, targeted U.S. personnel with explosives, served as bin Laden bodyguards, and acted as al Qaeda IED experts,” she said

Her office described three of them -- Abdel Qadir al-Mudafari, Mahmud Abd Al Aziz al-Mujahid and Majid Mahmud Abdu Ahmed – as former bin Laden bodyguards.

Her office said another, Zahar Omar Hamis bin Hamdoun, served as an Al Qaeda weapons and explosives instructor.

The Donald Trump campaign also criticized the transfers in a press release

The latest group of released prisoners mostly had been held without charge for some 14 years at Guantanamo. They were cleared for release by the Periodic Review Board, composed of representatives from six U.S. government agencies.

Some groups dispute the risk some of the inmates truly pose.

According to Amnesty, one of the Afghans released to the UAE alleged that he was "tortured and subjected to other cruel treatment" while in U.S. military custody. The man, identified only as Obaidullah, was captured by U.S. special forces in July 2002 and allegedly admitted to acquiring and planting anti-tank mines to target U.S. and other coalition forces in eastern Afghanistan.

In clearing him for transfer, the review board said he hasn't expressed any anti-U.S. sentiment or intent to re-engage in militant activities. However, a Pentagon detainee profile also said he provided little information and they had little "insight into his current mindset."

The review board is moving quickly.

Fox News reported earlier this month that 32 detainees are slated to have their cases heard by the board. Further, the 15 newly transferred detainees were among another 34 already slated for transfer -- another 19 detainees are expected to be transferred soon. 

Even as the administration accelerates the transfers, it still faces the thorny problem of figuring out what to do with prisoners that cannot be sent to other countries. The Defense Department has looked at prisons in Colorado, South Carolina and elsewhere, but Congress by law prevents Pentagon from bringing any of those detainees to the United States.

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.

Fox News’ Lucas Tomlinson and The Associated Press contributed to this report.