An explosion ripped through a football viewing centre in Damaturu, northern Nigeria, on Tuesday, residents said, as fans gathered to watch the World Cup.
The blast at the Crossfire venue, in the Nayi-Nawa area of the state capital of Yobe, happened at about 8:00 pm (1900 GMT), just as tournament hosts Brazil kicked off against Mexico.
There were no immediate reports of deaths but hospitals were reporting casualties being brought in, medical sources said.
A witness near the scene told Reuters they heard a loud boom. Some residents said they also heard a second explosion.
Damaturu, the capital of Yobe state, is an area that has been devastated by attacks from Islamist group Boko Haram which in April abducted more than 200 girls from a school in neighbouring Borno state.
The Nigerian government had advised residents to avoid gathering in public to watch the World Cup, concerned about possible attacks.