US air strike kills Afghan forces in friendly-fire incident

Afghan security forces were killed Friday in a U.S. military air strike in southern Afghanistan's Helmand province, the U.S. military said, calling the friendly-fire deaths "unfortunate" and pledging an investigation.

"We would like to express our deepest condolences to the families affected by this unfortunate incident," the U.S. military said in a statement, adding the Afghan government had already been notified about the strike on a compound in Helmand's Gereshk district, where the Afghan forces were gathered.

It did not say how many Afghans were believed to be killed.