A bomb blast at a site where Nigerian football (soccer) fans had gathered to watch the World Cup has killed at least 21 people.
Hospital sources said Wednesday that 27 others were injured in the blast, which took place late Tuesday in the northeastern town of Damaturu.
Scores of people had gathered at an outdoor viewing center to watch the match between Brazil and Mexico on large screens. So-called "viewing centers," where fans can watch the games for a small fee, are becoming a target for terrorists.
Witnesses say a bomb apparently hidden in a tricycle taxi exploded shortly after the match got under way.
There have been no claims of responsibility.
Damaturu is the capital of Yobe, one of three northeastern states that have been under a state of emergency following a string of deadly attacks linked to the Boko Haram Islamist militant group.
Last week, authorities in the states of Adamawa and Plateau ordered viewing centers closed because of fear of possible attacks.
In northeastern Nigeria, where the Boko Haram's five-year insurgency has killed thousands of people and crushed the economy, football is one of the few pleasures left.
A popular spectator sport
Boko Haram preaches its own harsh version of Islamic law that rejects all things Western, including football. But the sport remains hugely popular, with TV ratings indicating at least 17.5 million people in Nigeria alone watching Monday evening's scoreless World Cup match between Nigeria and Iran.
Free TV channels in Nigeria don't show the World Cup. But for about 25 cents, fans across the country can go to "viewing centers," which are often as informal as a television set and a bunch of chairs.
Tuesday night's bombing at the Yobe viewing station during the Brazil/Mexico World Cup match may deter some fans from watching at public gathering spots.
"Definitely I'm thinking of watching [World Cup matches] at home, because going to the viewing center has become something else with the recent bombing all over," said Beauty Zopti, a fan living in the neighboring northern state of Bauchi.
In late May, 40 people were killed watching a football match in Adamawa state, prompting a statewide ban on formal viewing centers. Two weeks earlier, in Plateau state, security forces stopped an attempted attack on a viewing center, but three people were still killed, including the bomber.
In recent months, the Boko Haram insurgency appears to have escalated, with more than 2,000 people killed this year alone and hundreds of schoolgirls kidnapped. Gunmen took more than 200 girls captive on April 14.
"Massacres have been occurring with regularity and some communities have actually been wiped out over the last six weeks," said Jibrin Ibrahim, executive director of the Center for Democracy and Development in Abuja, adding that "the insurgency is getting worse."
The United Nations says roughly half a million people have fled their homes because of the violence.