A bomb targeting Shia pilgrims observing the holy day of Ashoura has exploded in Yobe state in northeastern Nigeria killing dozens of people.

The blast happened on Monday in the city of Potiskum, as Shia Muslims were marking the religious occasion.

Conflicting reports quoting sources from the community said at least 32 people were killed. 

The worshippers were gathered outside a seminary in the Tsohuwar Kasuwa area of the city, after visiting the palace of the local emir, witness Ibrahim Maina and local police told the AFP news agency.

"It was a huge crowd and many of them were affected," the policemen told the AFP news agency. "The priority is to rescue the injured." 

They blew up the thing with dynamite

Emmanuel Ojukwu, Police spokesperson

The type of blast has not yet been confirmed, and no one has claimed responsibility for the attack.

In a separate incident on Sunday, gunmen armed with dynamite freed at least 50 inmates in a raid on a prison in central Nigeria's Kogi state, the same facility attacked by Boko Haram fighters in 2012, police said on Monday.

"They blew up the thing with dynamite," national police spokesman Emmanuel Ojukwu told AFP.

"Up to 50 inmates escaped," he said, but added that some had been re-arrested.

Local media have reported much higher figures for the number of prisoners freed.

The Koton Karfi prison in Kogi is thought to hold many suspected Boko Haram fighters, but Ojukwu said the raid was not linked to the five-year uprising, blaming it instead on "criminal activity".

Boko Haram, declared a "terrorist" organisation by Nigeria and the United States, has been fighting to create an Islamic state in Nigeria's mainly Muslim north.

Yobe is one of three northeastern states which was placed under emergency rule last year when the military launched a massive operation to crush the Boko Haram uprising.

More than 1,000 people have been killed in the region since the emergency measures were imposed, despite the enhanced military presence.

Source: AFP