At least five people have been killed after a car suicide bomb exploded at a checkpoint on the outskirts of Damaturu, capital of Yobe state on Monday.
The checkpoint is along a major highway that connects the city with Maiduguri, capital of Borno.
They were believed to be headed for the heart of town, but the insistence of the policemen to search their vehicle made the bombers detonate the explosives.
Last Friday, at least nine people were killed in Damaturu after two female suicide bombers detonated explosives at a prayer ground while Muslims were observing Eid.
About 500 people have been killed in insurgent attacks since the turn of the Buhari administration on May 29.