At least 10 people have been killed by cattle rustlers in the north-western state of Zamfara.
Villagers said dozens of armed men arrived on motorbikes, shooting dead members of a vigilante group set up to guard the area.
They made off with several cattle.
Communities in the north-west live in constant fear of attack.
Many have set up vigilante groups, saying the security forces are incapable of protecting them.
Zamfara has long faced problems with armed groups stealing cattle, kidnapping for ransom and attacking communities, which has in turn prompted some local people to form vigilante gangs.
More recently, there has been a growth in informal mining activity in this mineral-rich region, which has attracted people from outside the state, further fuelling instability.
At the beginning of April, the government responded to concerns over increasing levels of violence, suspended all mining activities in the state, and deploying additional troops to the area.
