JOHANNESBURG — In soccer-mad Nigeria, which is reaching fever pitch amid the World Cup tournament in Brazil, people often cram into viewing centers to watch games.

But Boko Haram, the northern Nigerian extremist group fighting for an Islamist state, has declared soccer to be “haram,” or sinful.

Officials on Wednesday said the group, or a similar splinter group, was suspected of being behind a blast a day earlier that killed at least 14 people and injured many more, including children, at an open-air World Cup viewing venue in Damaturu, capital of Yobe state.

No group immediately claimed responsibility for the attack.

Police Assistant Superintendent Nathan Cheghan said 26 people were wounded in the blast Tuesday night, which came as people watched Brazil play Mexico. There were concerns that the number of fatalities could rise.

Initial reports suggested the attack was a suicide blast in a three-wheeler rickshaw taxi. Authorities later reported that a vehicle loaded with explosives may have been abandoned near the venue. The blast follows several similar attacks in northern Nigeria in recent months.