Suspected Boko Haram bombers killed at least 54 people and wounded 143 in a series of bloody suicide attacks Saturday in Maiduguri, Nigeria.

The blasts occurred over four hours in locations from a busy fish market to a crowded bus station in the city, which is located in the northeast region of the country, Police Commissioner Element Adoda said.

Witnesses reported scenes of gore with mangled bodies and injured victims lying on the ground.

Maiduguri is the birthplace of the Islamic extremist group. The Nigerian military drove Boko Haram out of the city last year.

The deadliest blast occurred at the bustling Baga fish market, where at least 18 people were killed after a suicide bomber blew himself up in a rickshaw taxi near the entrance.

"I saw many dead bodies lying on the ground, many dead, and several others badly injured," fish seller Idi Idrisa said.

One hour later, a second explosion rocked the Post Office shopping area near the market, witness Baban Musa said. Musa reported many casualties.

Suicide bombers also blew themselves up at the Monday Market, the biggest in Maiduguri, and the Borno Express bus station.

The BBC quoted a witness as saying two female suicide bomber detonated devices at a security gate leading to the Monday Market. The BBC also reported that a teenager blew himself up at the bus station before security officials could stop him.

A fifth explosion shook a military checkpoint 50 miles outside the city. A soldier and two members of a civilian self-defense unit were wounded. The bomber apparently wanted to reach Maiduguri, said a police officer at the scene.

Although no one immediately claimed responsibility for the attacks, they bore the hallmarks of Boko Haram.

The extremists have tried to seize the city with armed assaults by hundreds of fighters and have made it the target for many bombings since they were driven from their base there after a military state of emergency was declared in May 2013.

Boko Haram has increased suicide bombings and village attacks in recent weeks as forces from Nigeria and Chad have driven the insurgents from a score of towns along Nigeria's border with Cameroon.

The insurgents also have attacked villages in Cameroon and Niger in response to Nigeria's neighbors forming a multinational force to confront the spreading Islamic uprising.

Chad's President Idris Deby this week said his forces know the whereabouts of Boko Haram leader Abubakar Shekau and warned him to surrender or face death.

Boko Haram fighters are massing at their headquarters in the northeastern town of Gwoza, in apparent preparation for a showdown with multinational forces, according to witnesses who escaped from the town.

An intelligence officer said they were aware of the movement but that the military is acting cautiously as many civilians still are trapped in the town and Boko Haram is laying land mines around it.

Maiduguri is the capital of Borno state and the biggest city in northeastern Nigeria, the heart of an Islamic uprising that has killed about 12,000 people in nearly six years.

The Associated Press contributed to this report.