The United States military says this week's deadly clashes with Taliban insurgents in northern Afghanistan "very likely" harmed civilians.
Thursday's pre-dawn joint counterinsurgency air strikes near the northern city of Kunduz killed at least 33 civilians, half of them children, provincial authorities said Saturday.
Two U.S. soldiers and several Afghan commando forces were killed before airstrikes were called, but the U.S. military until now had not spoken about possible collateral damage.
"An initial investigation has determined that efforts near Kunduz on November 3 to defend Afghan National Defense and Security Forces likely resulted in civilian casualties," U.S. military spokesman Brigadier General Charles Cleveland said at a news conference in Kabul.
He backed Afghan officials' assertions that U.S. forces had advised their local partners to undertake the operation in the Boz village to deter Taliban insurgents who were planning additional attacks in Kunduz city. Cleveland said the operation had eliminated several top Taliban commanders.
He promised the U.S. military, with the help of Afghan officials, would work to further investigate and determine the facts related to this event.
The spokesman defended the action, saying "every aspect" of this was clearly aimed at protecting the people of Kunduz.
"But every indication that we have right now is that the Taliban were firing on these friendly forces and every part of this was to defend those friendly forces," he said. "And what we know is that we have had Afghans who have been martyred, we have had Afghan soldiers who were wounded, and we have had American soldiers who were killed and American soldiers who were wounded."
General John Nicholson, commander of U.S. forces in Afghanistan, deeply regrets the loss of innocent lives, regardless of the circumstances, Cleveland said.
The civilian casualties have outraged residents in Kunduz, and they have staged street protests against it. Senior Afghan politicians, including ex-President Hamid Karzai, also criticized the U.S. military for causing the collateral damage.
Afghan Defense Ministry spokesman Dawlat Waziri, while addressing the same news conference, said the joint raid targeted senior Taliban leaders while they were conducting a war meeting.
Both Waziri and Cleveland condemned the Islamist insurgents for using their families as human shields during such activities.
"They conduct meetings in their own houses so if there are civilian casualties they can use it to say the government killed civilians," Waziri said, adding there were women and children of Taliban families among the dead.
But he would not discuss exact figures, nor did he confirm the 33 civilian deaths, saying investigations into the incident were continuing.
The Taliban has confirmed that three of its fighters were killed, but it has not immediately responded to allegations of using members' families as human shields.
The insurgents briefly captured Kunduz about one year ago.
The U.S. military, while conducting airstrikes in support of Afghan forces to evict the Taliban from the city at the time, mistakenly struck a hospital run by the medical charity Doctors Without Borders, known by its French acronym of MSF. The facility was destroyed, and more than 40 people were killed. Mainly, MSF doctors, staff, patients and their attendants were among the victims.