Police say gunmen have killed a policeman in a drive-by shooting in Nigeria's second-largest city.
Kano state police spokesman Magaji Musa Majiya said Monday six gunmen on motorcycles shot at a police station that had already been attacked twice this year.
A radical sect known as Boko Haram has launched similar attacks in an increasingly bloody campaign to fight Nigeria's weak central government.
Authorities also said Monday they shot dead six suspected Boko Haram members training at a camp in the northeastern town of Mubi.
The crackdown comes a day after the suicide bombing of a Catholic church in central Nigeria and retaliatory violence left 10 people dead.
Boko Haram, held responsible for killing more than 340 people this year alone, has claimed responsibility for church attacks in the past.