A GANG disguised in police uniforms opened fire on worshippers at a mosque in northern Nigeria this morning, 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 today, 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 neighbours, burning some of their victims’ bodies. Muslim groups also formed mobs and killed several Christians.

Boko Haram, blamed for killing more than 1,400 people in Nigeria since 2010, has repeatedly targeted the state and also attacked Muslims it accuses of not supporting its hardline interpretation of Islam.

But military spokesman Lieutenant Colonel Sani Usman told AFP that Sunday’s shooting was “a clear case of armed robbery,” and described it as a “revenge” attack linked to the rivalry between the thieves and the vigilantes.

Asked about a potential religious element in the shootings, he said only that “the victims were coming from prayers” at the mosque.

Village resident Dauda Maikudi told AFP that thieves regularly target the area as Dogon Dawa lies not far from a main road used by traders carrying goods and cash between the north and south of Africa’s most populous country.

“It was a pre-dawn raid,” he said. “The attackers… some of them dressed in police uniform, came into the village. They killed eight worshippers in the mosque and killed 13 other residents in the village.”

“We believe they were armed robbers because this area has been bedevilled by armed robbers for years,” he added.

Dogon Dawa lies about 70 kilometres (40 miles) from the state capital Kaduna city.