US drones fired two missiles into a compound in Pakistan's northwestern tribal belt Friday, killing at least nine militants and wounding more than five others, local security officials said. The attack took place in a village on the border of North and South Waziristan tribal areas, around 50 kilometres (30 miles) south of Miranshah. "Six drones were hovering in the sky at the time of the attack. One drone fired two missiles at a house," a security official in Miranshah told AFP. "At least nine militants were killed and more than five were injured in the strike. Their identities were not clear yet, but there may be some foreigners among them," he said. "The compound was completely destroyed. The militants had surrounded the area after the attack," the official added. A security official in the northwestern city of Peshawar confirmed the attack in the tribal belt, which is a notorious stronghold of Taliban and Al-Qaeda-linked militants. The covert strikes are publicly criticised by the Pakistani government as a violation of sovereignty but American officials believe they are a vital weapon in the war against Islamist militants. Few of the victims are publicly identified, but on January 3 Pakistani officials said warlord Mullah Nazir was killed in a strike on South Waziristan. He sent fighters into battle in Afghanistan and was accused of sheltering Al-Qaeda in South Waziristan. According to the London-based Bureau of Investigative Journalism, between 2,627 and 3,457 people have been reportedly killed by US drones in Pakistan since 2004, including between 475 and nearly 900 civilians.