The blast by a female teenager occurred in the market near the Old Elkanemi Cinema in the late afternoon, said Musa Danbaba, a member of a civilian protection militia. He said 34 bodies were counted and many more were wounded.
No group immediately claimed responsibility for the bombing, but it bears the hallmarks of Nigeria's Islamic extremist group, Boko Haram.
The Maiduguri market is where suicide bombers on Saturday detonated explosives that killed 54 people.
Last week, Boko Haram announced its allegiance to the Islamic State extremist group operating in Iraq and Syria.