Gunmen in the north-western Nigerian state of Katsina have killed 17 people, including five policemen, in separate attacks, the authorities say.
About 300 armed men on motorbikes targeted a police post in Kankara on Wednesday, shooting the officers dead.
They also killed at least three people in a nearby village.
In another incident, gunmen attacked several villages in Faskari district, killing nine people, looting supplies and stealing livestock.
Katsina, the home state of President Muhammadu Buhari, is one of the areas worst affected by violence in Nigeria.
The government is facing increasing criticism for failing to tackle security problems.