KADUNA, Nigeria – A gang disguised in police uniforms opened fire on worshippers at a mosque in northern Nigeria Sunday, killing at least 21 people, officials and residents said. The military and locals said the pre-dawn raid in the village of Dogon Dawa in Kaduna state was carried out by armed robbers engaged in a running feud with a local vigilante group. Having been repelled by the community militia last week, the gang returned Sunday, storming the mosque as people readied for early morning prayers, killing some victims inside the building and some outside. “We have 21 killed. Several others have been taken to the hospital with injuries,” said Musa Illela of the National Emergency Management Agency in Kaduna. Religiously divided Kaduna has been rocked by waves of sectarian violence in recent months. Suicide bombings at three churches in June that were claimed by Islamist group Boko Haram sparked reprisal violence by Christian mobs who killed dozens of their Muslim neighbors, burning some of their victims' bodies. Muslim groups also formed mobs and killed several Christians. Boko Haram has repeatedly targeted the state and also attacked Muslims it accuses of not supporting its hardline interpretation of Islam. – Reuters