The Afghan government released 65 detainees on Thursday who the United States has warned pose a serious security threat, a move that further strains already tense US-Afghan ties as the international mission in Afghanistan winds down.
Afghan Defense Ministry spokesman Zahir Azimi said the prisoners had been released from a detention facility near the Afghan capital, Kabul, and would be sent back to their respective home areas throughout Afghanistan.
The US embassy called it a "deeply regrettable" move that ran counter to a 2012 agreement on detainees.
"The Afghan government bears responsibility for the results of its decision," the embassy said in a statement.
Abdul Shakor Dadras, head of the Afghan board charged with reviewing the prisoners' cases, said their detention had been unjustified from the outset, despite information put forward by the United States.
"We could not find any evidence to prove that these 65 people are criminals, according to Afghan law," Dadras told Reuters Television.
"I believe the release of these 65 people will benefit the Afghan nation, and it will benefit the American nation and American government."
The prisoners were transferred to Afghan authority last year as part of the US and NATO transition out of Afghanistan. A coalition of foreign forces has been battling the Taliban since the Islamist group was ousted in 2001.
The fate of another 23 prisoners who the United States contends should not be released is being examined by the Afghan government, the US official said.
The US military has said the released men should be tried in Afghan courts.
"Detainees from this group of 65 are directly linked to attacks killing or wounding 32 US or coalition personnel, and 23 Afghan security personnel or civilians," the US military said in a statement.
A US military official, speaking on condition of anonymity, said the United States had provided Afghan officials with "hundreds of pages" of what he described as "hard evidence" or investigative leads against the prisoners.
Some of the detainees, he said, had been linked by biometric data to the production or placement of improvised explosive devices (IEDs), sometimes through fingerprints left on adhesive tape used to assemble homemade bombs.
More tension between Kabul, Washington
The detainees have become one more issue fuelling tension in US-Afghan ties ahead of a presidential election in April and the planned pullout of most foreign troops by the end of the year.
The Obama administration has been pressing Afghan President Hamid Karzai for months to sign a bilateral security agreement with Washington that would allow some US troops to stay beyond that deadline.
The United States says the prisoners released on Thursday could now pose a threat to Afghan civilians.
Last week, the United Nations said that civilian deaths had increased in 2013, as fighting intensified between government forces and insurgents. The U.N. said that bombs accounted for a third of the total civilian death toll.
While US officials have said that US forces would try to kill or capture the men if they took up arms against them, it remains unclear if US or coalition forces would try to apprehend or target them pre-emptively.
(Writing by Missy Ryan; Editing by Paul Tait and Ron Popeski)