A bomb blast at a busy market in Nigeria's northeastern city of Maiduguri has killed about 50 people, according to witnesses and hospital sources.  

There was no immediate claim of responsibility for Tuesday's explosion in the Gamboru cattle market, but there have been repeated attacks by the armed group Boko Haram in Maiduguri and the rest of Borno State.

A military source told the Reuters news agency that the bomb, which was concealed under a butcher's table in the market, went off at around 1pm, killing shoppers and passersby.

 

The market is visited by hundreds of people every day.

A 12-hour curfew was imposed in the city overnight.

Other attacks blamed on Boko Haram, including on a mosque, killed more than 30 people in Maiduguri over the weekend.

The violence poses a great challenge to the country's new president, Muhammadu Buhari, who announced on Friday that he is moving the military's headquarters from the capital Abuja to Maiduguri to better tackle Boko Haram.

Boka Haram video

Boko Haram released a new video on Tuesday that allegedly shows fighters shooting wounded Nigerian soldiers in the head and beheading a man in civilian clothes as well as charred parts claimed to be the remnants of a downed Nigerian jet fighter.

The video, the first released since the group pledged allegiance to the Islamic State of Iraq and the Levant (ISIL) group, has no sign of longtime leader Abubakar Shekau, previously a mainstay of the group's videos.

In the video, a member of the group say Boko Haram still holds several northeastern towns and has thousands of fighters - claims impossible to substantiate.

The video gloats over alleged disunity in the multinational force that in March announced it had driven Boko Haram from all towns and villages.

Nigerian neighbours Chad and Niger have said the fight against Boko Haram would be long over if they had better cooperation from Nigeria.

The new president is travelling to Chad and Niger on Wednesday on his first official trip outside Nigeria, spokesman Garba Shehu said.

Boko Haram's violent campaign has killed about 13,000 people since 2009 and driven 1.5 million from their homes.

Source: Al Jazeera and agencies