Gunmen in north-west Nigeria have stormed a mosque, killing Muslim worshippers in what the local government has called a "reprisal attack". Police in Katsina state said 17 worshippers were shot dead by the assailants - known locally as bandits - but other reports from the region say the death toll is higher.

ABUJA, Nigeria -- Gunmen attacked a mosque in northwestern Nigeria on Tuesday morning, killing at least 13 people during morning prayers, local authorities said.