Afghan officials said a U.S. airstrike Monday killed an undetermined number of militants and at least 12 civilians in western Afghanistan.
U.S. officials said the strike in the Gozara district of Herat province killed 15 militants and targeted Taliban leader Ghulam Yahya Akbari.
They have not commented on the reported civilian deaths, but promised to investigate. In a statement, U.S. officials also said it has been a past practice of insurgents to surround themselves with women and children.
Images reportedly from the area show the body of a young boy, dead animals and destroyed tents.
Regional police officials said the attack targeted a group of people living in tents in the remote Afghan countryside.
Afghan President Hamid Karzai has said civilian deaths are undermining the Afghan people's support for international troops.
On Tuesday, the United Nations said 2,118 civilians were killed last year in Afghanistan - the highest number since the U.S.-led invasion toppled the Taliban government in 2001.
The report said militants are responsible for 55 percent of the civilian casualties, while Afghan and foreign troops are responsible for 39 percent.
Some information for this report was provided by AP and Reuters.