NATO airstrikes killed Afghan civilians in two provinces, local officials reported Monday, and the U.S.-led coalition said it plans an apology in one of the incidents.

An airstrike Friday killed six members of a family in the Sangin area of southern Helmand province, according to the provincial spokesman.

The strike was called in after insurgents attacked foreign and Afghan forces in the area, he said in a statement. Helmand’s governor called the incident a mistake.

“At this point in the investigation, we are able to confirm the incident and will be formally apologizing in the next couple of days to the family,” said Lt. Col. Stewart Upton, a spokesman for NATO’s International Security Assistance Force (ISAF) in Afghanistan. “We are deeply saddened by any civilian deaths, and particularly regret incidents where civilians are killed as a result of actions by ISAF.”

There were conflicting accounts on the number of deaths in another incident in Bala Murghab district of northwestern Badghis province, where unconfirmed reports put the civilian deaths at 14.

The Badghis provincial governor, Dilbar Jan Arman, confirmed the loss of civilian lives in Sunday’s incident, but he said he did not have further details or an exact death toll.

Civilian deaths have been a key source of tension between President Hamid Karzai and U.S.-led forces fighting the resurgent Taliban in Afghanistan.

The casualties are undermining efforts by Karzai, NATO and, in particular, the United States to win the hearts and minds of ordinary Afghans in the more than decade-long unpopular war.

Separately, Afghan forces were locked in hours of fighting with a group of insurgents who attacked key government buildings overnight in Sharan, the provincial capital of Paktika province near the border with Pakistan.

There were no casualties among the Afghan forces from the attack, which resulted in the deaths of three assailants, officials said.

Civilian deaths also took place in northern Sar-e Pol province, where floods caused by heavy rains destroyed or damaged dozens of mud-built houses in several villages Sunday night, lawmakers from the province said.

Among the 24 who perished in the disaster were villagers attending a wedding party in the rugged region, the lawmakers said. An undetermined number of people were missing.

A rescue operation was underway, said Mohammad Sediq Hassani, a senior official at the national disaster management department in Kabul. He said emergency aid was flown by two helicopters to the affected villages, which are among the poorest in Afghanistan and prone to annual natural disasters.

Correspondent Kevin Sieff contributed to this report.