At least 51 people have been killed and more than 100 injured in three bombings in the northeastern Nigerian town of Maiduguri.

Saturday's triple blasts were the worst attack on the city since suspected Boko Haram fighters failed in their bid to seize it at the end of January.

Witnesses said two explosions targeted a market on Saturday.

Witness Baban Musa told The Associated Press that the second explosion occurred at the busy shopping area called Post Office, close to the fish market where the suicide bomber struck earlier Saturday morning.

Al Jazeera's Ahmed Idris in the capital Abuja said at least 15 people were killed in the fish market blast according to witnesses.

Moments after the two blasts a third explosion was heard close to the market.

"I have counted five ambulances that have evacuated victims from the scene. Soldiers are shooting in the air and warding off people at the market," Salisu Yaya, a member of a civilian task force, told Reuters news agency.

Maiduguri is the state capital of Borno, the heartland of the armed group Boko Haram which has long coveted the city as the capital of an Islamic state they want to carve out of religiously mixed Nigeria.