Updated

Police say armed robbers have shot and killed 48 people in a revenge attack on villagers in northwest Nigeria who have formed vigilante groups to try to end a spree of violent thefts.

Police Commissioner Akila Usman of Zamfara state said the gunmen arrived on motorbikes Tuesday night and went from house to house in Kizara village.

The gunmen searched for suspected vigilantes and shot them and their families. Usman said among the dead were the chief imam, or religious leader, as well as a man believed to be the head of the vigilante group.

Nigeria's Zamfara state is notorious for deadly armed robberies.