At least 18 people were killed late Wednesday when four suicide bombers blew themselves up in a town in north-east Nigeria, authorities in the state of Borno said.
The first blast took place at a prayer ground in Konduga, near the city of Maiduguri, while the others took place nearby. The attackers, two men and two women, were among the dead.
At least 29 people were seriously injured and taken to hospital.
The Sunni fundamentalist terrorist group Boko Haram was thought to be behind the attack.
At least 20,000 people have died in the region since 2009 in attacks staged by the group.