Nigerian police say a female suicide bomber has killed at least five people in an attack at the entrance to bus station in the northeastern town of Damaturu.
At least 28 others were wounded in the early Tuesday morning blast.
No one has claimed responsibility for the attack, but militant group Boko Haram has used girls and women in recent suicide bombings in the region, raising fears it is using kidnap victims.
Nearly 300 schoolgirls were kidnapped during a Boko Haram raid on a small town in the northeast last year. More than 200 of the girls are still missing.
Boko Haram, which recently pledged allegiance to the militant group Islamic State, has killed more than 10,000 Nigerians as part of a campaign to impose Islamic rule on northern Nigeria.
Nigeria's president Muhammadu Buhari has ordered the military to defeat the Boko Haram insurgency within three months.
