Witnesses report hearing multiple explosions and gunfire in Kano, the largest city in northern Nigeria.

Nigerian state television reports that a suicide car bomber attacked a police headquarters in the city Friday, wounding several people. The TV station also reports attacks on a police station and an immigration office.

Reports from Kano say the blast at the police headquarters ripped the roof off the building.

A local journalist told VOA that he heard gunfire after the blasts and saw wounded people being carried out of one of the police stations.

Nigeria is trying to cope with a wave of bombings and shootings in the north, most of it blamed on the radical Islamist sect Boko Haram. The shadowy group has claimed responsibility for several of the deadly attacks.

President Goodluck Jonathan has vowed to crush the group. Last month, he declared a state of emergency in 15 areas and deployed troops in an effort to maintain order.