NATO was investigating reports that its planes killed 14 members of an Afghan civilian road construction crew while hunting Taliban fighters in a mountainous region.
Initial reports from Afghan officials blamed U.S.-led coalition forces and said 22 people had died.
The North Atlantic Treaty Organization's International Security Assistance Force said it conducted airstrikes against Taliban fighters in Nuristan province Monday night.
At a news conference, spokesman Brig. Gen. Carlos Branco said: "The situation is not clear at all at this stage. We are carrying out the investigation and trying to get a clear picture."
Afghan officials said bombs hit two tents housing Afghan engineers and laborers contracted by the U.S. military to build a road.