KABUL (Reuters) - A foreign airstrike killed nine Afghan policemen in western Afghanistan overnight after a clash in which both sides mistook the other for Taliban armed groups,

Afghan officials said yesterday.The incident is certain to reinforce Afghan perceptions that international troops do not take enough care to avoid hurting innocents and comes after a string of mistakes that Afghan officials say killed dozens of civilians.Clashes broke out between Afghan police and international troops in the Anar Dara district of Farah province, with both sides thinking the other were Taliban militants, the deputy provincial governor Mohammad Younus Rasuli said. The foreign troops called in airstrikes on the police post that killed nine policemen and wounded four others, including the district police chief, he said.Both NATO's International Security Assistance Force (ISAF) and the separate US-led coalition force in Afghanistan said they were aware of an incident in Farah, but could not confirm any details of what had happened.