A NATO helicopter strike targeting missile-launching Taliban militants killed four civilians in western Afghanistan, an Afghan official said today.
NATO said they were investigating the attack.
The attack in western Herat province comes as civilian casualties from NATO attacks remain a contentious issue across the country as international troops prepare to withdraw by the end of this year.
Almost 200 people protested against NATO in Herat today, carrying the bodies of the dead civilians into the provincial capital and demanding an investigation.
The strike happened last night in the province's Shindan district, said Raouf Ahmadi, a spokesman for the provincial chief of police. He said Taliban militants launched a missile at an airport nearby, drawing the NATO helicopter's fire. He said the NATO attack killed two men, one woman and a child.
In a statement, NATO said it was aware of the attack and was investigating, without elaborating.
NATO "takes all allegations of civilian casualties seriously, and is assessing the facts surrounding this incident," it said.
Civilians increasingly find themselves under fire as the 2001 US-led war draws to a close, as Afghan forces take the lead in operations targeting the Taliban.
The civilian death toll in the war in Afghanistan rose 17 per cent for the first half of this year, the United Nations reported in July. The UN said 1,564 civilians were killed from January through June, compared with 1,342 in the first six months of 2013.
Insurgents were responsible for 74 per cent of the casualties, the UN said, while pro-government forces were responsible for 9 per cent, government forces 8 per cent and foreign troops just 1 per cent. The rest could not be attributed to any group.
Outgoing President Hamid Karzai has repeatedly clashed with NATO over civilian casualties.
Afghan security forces also increasingly find themselves under attack as the planned foreign troop withdrawal draws near. Today, a police car struck a roadside bomb in the eastern province of Nouristan, killing three officers, provincial police chief Abdul Baqi Nouristani said.
