The blast took place when a suicide bomber on a motorized tricycle detonated himself in the north-eastern Nigerian city of Maiduguri.
"The bomber failed to ram an 18-seat bus at about 8 a.m. as the vehicle moved out of a station in the city, said Hassan Ibrahim, a pro-government militia member.
"The suicide bomber could not gain enough momentum to get to the traveling bus," Ibrahim said by phone from Maiduguri.
Violence has escalated in Nigeria, the largest economy of Africa since President Muhammadu Buhari took office on May 29.
At least 44 people were killed by two bombs that exploded at a crowded mosque and an elite Muslim restaurant in Nigeria's central city of Jos recently.
Maiduguri is the birth place of Boko Haram, which has created havoc in the forms of murder and kidnaping during its six-year campaign to carve out an Islamist state in northern Nigeria.