Some people at the scene told Reuters an attacker dropped a device in front of the venue on Tuesday night in the town of Damaturu and ran off, while others said it was the work of a suicide bomber.
No one claimed responsibility for the blast, but Damaturu and the surrounding Yobe state are at the heart of a five-year-old insurgency by Islamist group Boko Haram.
The group was blamed for a an attack on another venue screening matches in the north-eastern state of Adamawa that killed at least 14 people and wounded 12..
A Reuters reporter at Damaturu's General Sani Abacha Specialist Hospital counted 13 people dead - including small children - and at least 20 wounded.
The Nigerian government has advised people to avoid gathering in public to watch the World Cup, concerned about potential attacks.
Many fans in football-mad Africa rely on informal venues - often open-sided structures with televisions set up in shops and side streets - to watch live coverage of the sport.
Boko Haram - whose name roughly translates as "Western education is sinful" - has declared war on all signs of what it sees as corrupting Western influence.
The group has killed thousands in its push to carve out an Islamic state in religiously-mixed Nigeria.
- Unrest, Conflicts & War