At least 70 civilians were killed and 20 others wounded on Saturday by attackers in the Nigerien villages of Tchombangou and Zaroumdareye in western Tillabery region in Niger.
The attack happened close to the border with Mali, security sources said on Sunday.
The attackers, who came in large numbers on motorcycles, carried out the massacre in retaliation after two members of their group were killed by villagers while committing an attack earlier in the day, the same sources said.
This part of Niger has, in recent years, suffered from deadly attacks.