At least 12 people died at a police station in Gombe Friday in an attack police said they believe was carried out by the militant Islamic group Boko Haram, Voice of America reported.
Officials said four civilians were among the dead and police and army officers were among the injured, the BBC reported.
Police said they defended a second attack at a prison.
Officials said a motorcyclist armed with a gun killed five people at a mosque in Kano Friday. Although no one claimed responsibility for the attack, police said they think Boko Haram was involved.
Boko Haram has been responsible for violent attacks in its effort to implement Shariah law in Nigeria, which is divided between Muslims in the north and Christians in the south.