Authorities say at least five police officers have been killed in separate attacks in northern Nigeria.

Gunmen raided Birnin-Gwari in Kaduna state late Wednesday, attacking a police station and using explosives to enter two banks in the area. Kaduna state police spokesman Aminu Lawan said Thursday that three police officers had been killed during the attack, which authorities believe was the work of a criminal gang.

In Gombe state in Nigeria's northeast, police say gunmen suspected to belong to a radical Islamist sect known as Boko Haram killed two officers at a checkpoint early Thursday morning.

The attacks come as Boko Haram launches attacks against Nigeria's weak central government. The bloodshed continues unstopped, despite the deployment of extra police officers and soldiers to the region.