KABUL (Reuters) - The top American general in Afghanistan promised on Saturday an investigation into civilian casualties caused by an air strike in support of Afghan special forces and their U.S. advisors near the northern city of Kunduz this week.

Incoming Commander of Resolute Support forces and U.S. forces in Afghanistan, U.S. Army General John Nicholson speaks during a change of command ceremony in Resolute Support headquarters in Kabul, Afghanistan, March 2, 2016. REUTERS/Rahmat Gul/Pool

More than 30 civilians, half of them children, were killed on Thursday after a strike on the village of Buz Kandahari, just outside Kunduz, that was called in when a special forces raid encountered heavy fire from Taliban militants.

General John Nicholson, commander of U.S. forces in Afghanistan, said he deeply regretted the loss of innocent lives.

“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,” he said in a statement.

“We will work with our Afghan partners to investigate and determine the facts and we will work with the Government of Afghanistan to provide assistance.”

The raid targeted three Taliban leaders in the village, who officials said were planning attacks on Kunduz. It met “significant enemy fire from multiple locations” and called in support from U.S. aircraft.

Afghan officials said 33 civilians, including 17 children, appeared to have been killed.

The intensity of the fighting, in which three members of the Afghan special forces and two U.S. advisors were also killed, underlined how precarious the situation around Kunduz remains, a month after the insurgents threatened to overrun the city.

Defence Ministry spokesman Dawlat Waziri said the Taliban militants targeted in the raid were senior figures in the movement who had been targeted in their own houses.

“They weren’t ordinary people who had gathered. They were leading fighting in Kunduz. They were the commanders of their military commission,” he told a news conference, adding that they were evidently willing to use their own family members as human shields.

“They hold meetings in their own houses and if there are civilian casualties, it’s an achievement for them because they can say the government killed civilians,” he said.