KABUL The NATO-led force in Afghanistan said it was investigating whether its troops had inadvertently killed three Afghan civilians on Wednesday while its forces fought insurgents in the south of the country.
Civilian casualties caused by foreign forces hunting militants have long been a major source of tension between President Hamid Karzai and the West, especially the United States, and led to a falling-out with Washington last year.
Rules governing the use of air strikes by NATO and U.S. aircraft have been tightened considerably in the past year in response, but incidents still emerge intermittently.
On Wednesday, the NATO-led International Security Assistance Force (ISAF) said in a statement it was "looking into the possibility that three Afghan civilians were inadvertently killed and one wounded by ISAF forces" during fighting with insurgents in the Sangin district of Helmand province.
It said four Afghan civilians had been brought to a nearby ISAF base after the fighting and that three of them had subsequently died.
Helmand is one of the Taliban's traditional strongholds in the south and was the launching point for a major counter-offensive by ISAF troops last year.
ISAF commanders say security has improved in some parts of Helmand but fighting persists in many areas.
In a mid-year report, the United Nations said civilian casualties had risen 31 percent in the first six months of 2010 compared with the same period last year, with more than three-quarters of the deaths blamed on insurgents.
In contrast, deaths attributed to "pro-government" forces -- Afghan and foreign troops -- fell sharply, the U.N. report said, largely because commanders had tightened the rules governing the use of air strikes.
Violence across Afghanistan, however, is at its worst since the Taliban were ousted by U.S.-backed Afghan forces in 2001, with civilian and military deaths at record levels despite the presence of about 150,000 foreign troops.