KABUL , Afghanistan ( CNN ) -- Thirteen people , described by the U.S. military as `` noncombatants , '' were killed in western Afghanistan earlier this week during a coalition operation , the military said Saturday . An Afghan man grieves for his brother after an attack this week by U.S.-led coalition forces . `` We expressed our deepest condolences to the survivors of the noncombatants who were killed during this operation , '' said Brig . Gen. Michael Ryan , U.S. Forces-Afghanistan . Three militants also died in Tuesday 's operation in the Gozara district of Herat province , the military said . The killings further inflame Afghans ' anger and frustration over the killing of civilians in U.S.-led coalition and NATO operations . Many civilians also die in the crossfire between coalition forces and Taliban militants . Watch the challenge coalition forces face » . Afghan and coalition investigators and international observers this week were in Herat this week . Weapons and ammunition were found at the site of the operation and Afghan soldiers held shuras , or consultative bodies , with village leaders . Ryan discussed the attack with senior police and army officials and with the governor of Herat . `` Our inquiry in Herat demonstrates how seriously we take our responsibility in conducting operations against militant targets and the occurrence of noncombatant casualties , '' Ryan said . `` Our concern is for the security of the Afghan people . To this end , we continually evaluate the operations we conduct during the course of our mission in Afghanistan and have agreed to coordinate our efforts jointly . '' President Hamid Karzai raised the issue of civilian casualties during a meeting he had on Saturday with visiting U.S. House Speaker Nancy Pelosi . A `` recent consensus between the Afghan government and NATO , which gives more authority to the Afghan security forces during military operations , house searches and detention of suspected individuals , will help in reducing civilian casualties and bringing more effectiveness in the fight against terrorism , '' Karzai said .
Military operation kills 13 civilians , three militants , U.S. says . Coalition offers condolences , helps identify victims . Weapons and ammunition found at site of attack . Comment: