Violence rocked the Nigerian capital of Abuja on Wednesday when a bomb exploded at a shopping mall in the upscale Wuse 2 neighborhood, killing at least 21 people and sending a pall of black smoke into the sky.
Police confirmed the preliminary death toll and said 17 people were injured in the blast at the Emab Plaza mall.
The explosive device was placed amid a group of vehicles near the entrance to the center, according to witnesses cited in local media accounts. Among the dead were street vendors who were selling food and other goods nearby.
"Our most important assignment now is to secure lives, secure the crime scene," police spokesman Frank Mba said at the explosion site.
The blast follows two bomb attacks that killed at least 120 people in Abuja earlier this year, both of them in the neighborhood of Nyanya, on the outskirts of the city.
No group has claimed responsibility for the latest attack, but suspicion fell on Boko Haram, the violent group that has been fighting for over a decade for the creation of an Islamic state in Nigeria.
Boko Haram opposes Western education, culture and democracy. The insurgency has turned the country's north into a war zone, closed down schools, devastated the regional economy and killed some 12,000 people since 2009.
Boko Haram militants have been blamed for a series of bombings across Nigeria, including an attack Monday at a medical college in the northern city of Kano that killed eight people.
Last week, at least 14 people were killed in an attack on a World Cup soccer viewing venue in Damaturu, capital of the northern state of Yobe. In May, about 130 people were killed in twin explosions at a market in Jos, in central Nigeria.
Nigerian authorities seem incapable of crushing the insurgency and restoring security.
Boko Haram's seizure of 395 schoolgirls from the northeastern village of Chibok in April has focused attention on corruption and incompetence in the country's military. More than 170 of the girls have escaped, but government officials say 219 remain unaccounted for.