An explosion has struck a venue in the town of Damaturu in northeast Nigeria where fans had gathered to watch a World Cup football match, police say.
There were reports that a suicide bomber detonated a tricycle packed with explosives at the venue.
There was no official word on casualties from Tuesday night's blast at the Crossfire venue in the Nayi-Nawa area of the town.
Al Jazeera's Ahmed Idris, reporting from Abuja, said hospital sources had confirmed that several people had died.
"Emergency workers are telling us that people are avoiding the scene of the accident for fear of a secondary explosive device," he said.
A witness near the scene told Reuters news agency they heard a loud boom. Some residents said they also heard a second explosion.
Sanusi Ruf'ai, police commissioner for Yobe state, told AFP: "There was an explosion outside a soccer viewing centre here in Damaturu at around 8.15pm. "Our men have deployed to the scene but it's too early for us to give details."
Damaturu is the capital of Yobe state, an area that has been devastated by attacks from rebel group Boko Haram which in April abducted more than 200 girls from a school in neighbouring Borno state.
Viewing centres closed
The Nigerian government had advised residents to avoid gathering in public to watch the World Cup, concerned about possible attacks, even issuing a direct warning two days ago to close down all viewing centres.
|The origins of Nigeria's Boko Haram
Authorities in Adamawa, in northeast Nigeria, last week closed viewing centres, where large crowds gather to watch matches on the big screen, while the central state of Plateau followed suit days later.
Earlier this month, at least 40 people were killed when a bomb went off after a football match in the town of Mubi in Adamawa. The apparent target was fans trying to leave after the final whistle.
In May, three people were killed in a blast outside a viewing centre showing the European Champions League final between Real Madrid and Atletico Madrid in Jos, the capital of Plateau state.
In April, suspected Boko Haram members stormed a packed venue in Potiskum, in northeast Yobe state, shooting dead two people as they watched Champions League quarter-final matches.
While no one has claimed responsibility for the attack, Idris said authorities would be likely to blame Boko Haram.
"Definitely the finger of blame will point to that particular group," Idris said.
Boko Haram has killed thousands since 2009 in its push to carve out an Islamic state in Nigeria's north.
Source: Al Jazeera and agencies