NATO has confirmed that American troops enlisted with the Western military alliance killed 33 civilians in a single incident in Afghanistan’s volatile north back in November last year.

The military alliance’s Afghan Resolute Support Mission made the admission in a report on Thursday. The acknowledgement came after a US military probe into the incident officially revealed the perpetrators behind the carnage, which occurred near Kunduz on November 3 last year.

“The investigation determined, regretfully, that 33 civilians were killed and 27 others wounded,” NATO said in the report, referring to the US probe.

The deadly incident, which is considered one of the most contentious ones involving US-led NATO forces during 15 years of their military campaign in Afghanistan, took place when NATO ground forces called in an airstrike against Taliban militants holed up inside civilian homes in the Buz Kandahari Village in the vicinity of Kunduz.

Civilian men, women and children were “likely inside the buildings from which the Taliban were firing,” the NATO report said, adding that two US troops and three Afghan commandoes had also been killed in the firefight.

Following the attack, angry local people took corpses to the local governor’s offices to show their anger and staged a protest demonstration.

Three days after the violence, the United Nations Assistance Mission in Afghanistan (UNAMA) censured the loss of civilian lives during the US-led operation in the village and announced that it had launched an investigation into the incident. The findings of the UN probe are due to be released by the end of this month.

Meanwhile, the US investigation has cleared the troopers involved in the attack, who it said had acted in “self-defense.”

Taliban militants briefly overran the city of Kunduz, the provincial capital of the same name, in early October last year. They had briefly seized control of the city a year earlier but had been pushed out of Kunduz weeks later.

Taliban militants were removed from power following the 2001 US-led invasion of Afghanistan, but have stepped up their activities in recent months, attempting to overrun several provinces. Their militancy continues, however, despite the presence of NATO troops.