Witnesses reported gunshots and explosions early Wednesday in the northern Nigerian city, Kano, where Islamist insurgents have staged a series of deadly attacks in recent months.

Local residents and journalists reported hearing several loud explosions followed by an extended period of gunfire just before early morning prayers in the largely Muslim city. There were no immediate reports of casualties. Security officials refused to comment on the situation.

Kano, Nigeria's second-largest city, has seen continued flare-ups in violence since members of the radical Islamist sect known as Boko Haram killed at least 185 people in a series of coordinated attacks there last month.

Authorities imposed a dusk-to-dawn curfew in Kano following the attacks.

Boko Haram has said it wants strict Islamic law to be imposed across Nigeria, which is divided between the mostly Muslim north and largely Christian south. But some analysts say some of the violence also appears to stem from political disputes.