Up to 13 civilians, mostly women and children, were killed in a NATO airstrike on Thursday in the eastern Afghan province of Khost, provincial police chief Mohamad Zazai said. "Unfortunately eight women, four children, and one man were killed in a NATO airstrike on a residential house in Dowamanda district early this morning," Zazai said. He said four militants from the Taliban-linked Haqqani network were also killed in the strike. "The body of a Haqqani commander and three fighters have also been recovered from the vicinity of the house. A delegation has been sent to investigate the incident," he said. A spokesman for the provincial governor confirmed that civilians had been killed in the incident but gave no further details. NATO's International Security Assistance Force said those killed were family members of the Haqqani network, which is a target of the alliance force. A spokesman for the coalition said Afghan-led forces had gone in search of the insurgents when they came under attack by rocket-propelled grenades and small-arms fire. "Responding to the insurgent attack, the security forces returned fire and called in an air weapons team. The subsequent air strike killed several insurgents and unintentionally a number of associated family members," the spokesman said. The deaths triggered protests that blocked the main highway to Kabul nearby. They come a day after provincial authorities in southern Ghazni claimed two civilians were killed in another military incident. NATO said it was looking into those claims.