KABUL, Afghanistan — The NATO mission in Afghanistan has opened a preliminary investigation into claims that more than 20 civilians were killed in recent American airstrikes in the southern province of Helmand, military officials said Saturday.

Elders from the Sangin district, the scene of heavy fighting in recent weeks, with the Taliban blowing up Afghan Army posts there, have said that multiple American airstrikes early Friday morning killed at least 22 civilians, including several women and children.

Brig. Gen. Charles H. Cleveland, a spokesman for the American-led NATO mission, insisted that the military command had seen no conclusive evidence that civilians were killed in the airstrikes, but said that “a formal review to determine the credibility of the claims” had been opened. The investigation team involved NATO officers outside the American command to ensure impartiality, he added.

“We are absolutely investigating this, and we take claims of civilian casualties seriously, although at this point we have no indication at all that civilians were killed,” General Cleveland said.