An explosion rocked a venue in the town of Damaturu in northeast Nigeria where fans had gathered to watch a World Cup soccer match on Tuesday, a security source said.
There was no immediate word on casualties but a Reuters witness near the scene heard a loud boom. Some residents said they also heard a second explosion.
Damaturu is the capital of Yobe state, an area that has been devastated by attacks from militant Islamist group Boko Haram which in April abducted more than 200 girls from a school in neighboring Borno state.
The Nigerian government has advised residents to avoid gathering in public to watch the World Cup, concerned about possible attacks.
Boko Haram has killed thousands since 2009 in its push to carve out an Islamic state in Nigeria's restive north.