At least three civilians were killed along with 14 insurgents in a Nato air strike targeting a senior Taliban commander in southern Helmand province.
The raid comes only a day after another air strike by foreign forces targeting insurgents in Helmand which Afghan police said killed civilians.
Deaths of civilians in Nato attacks have fuelled tensions between Afghan president Hamid Karzai and his Western allies, who are under increasing pressure at home over the unpopular war.
The strike on a compound killed 14 insurgents and three civilians, said provincial police intelligence chief Kamaluddin.
A spokesman for the Nato-led International Security Assistance Force (ISAF) said it was investigating the report of a strike, but did not have any information.
At least three Afghan civilians were killed along with 17 insurgents in a Nato air strike in Helmand yesterday, police said. ISAF said it was aware of the reports of civilian casualties but declined immediate comment.
Civilians are killed by both sides in the conflict, but the war is now in its bloodiest year since the 2001 US-led invasion that ousted the Taliban from power.
Reuters