An explosion went off on Tuesday at a shopping centre in the Nigerian capital Abuja, where an unexploded bomb was later discovered, rescue officials said.
The first blast happened at roughly 9:00 pm at a shopping plaza in the city's Wuse II district, spokesman for the National Emergency Management Agency (NEMA), Yushau A. Shuaib, said in a statement.
Rescue workers then rushed to the scene and cordoned off the area, where the unexploded bomb was discovered, an official said.
"When we were trying to find out what is happening, the anti-bomb squad discovered another one. They just detonated it," the head of NEMA's Abuja office, Ishaya Chonoko, told journalists at the scene.
"The good thing is that there was no report of human casualty," he added.
An AFP reporter said the area was swarming with rescue workers from several emergency services, but that journalists were being kept several hundred meters (yards) back and so it was not possible to survey any potential damage.
The shopping centre is located in a commercial district of Abuja and is not particularly close to any major government buildings.
Nigeria's Boko Haram Islamists, responsible for scores of attacks in recent months, have previously struck targets in and around the capital.
A suicide bomb attack on UN headquarters in Abuja in August killed at least 25 people, while another at the Abuja office of one of the country's most prominent newspapers left four dead.
Most recently, on June 22, a blast went off outside a nightclub in Abuja that shattered the windows of nearby buildings but caused no casualties.
A police statement said the late Tuesday blast occurred "near" the Banex Plaza shopping mall, calling it "a low level explosion."
"The incident had a zero casualty record -- no life lost, no person injured and no car damaged or burned," explained the statement from national police spokesman Frank Mba.
He warned "mischief makers" against trying to sow further chaos in the capital of Africa's most populous nation and said "intensive patrols" were ongoing around the city.
Much of Boko Haram's violence has been concentrated in northern Nigeria, particularly in the northeast where they are believed to be based.
The group's deadliest attack yet occurred on January 20 in the northern city of Kano, the country's second-largest, when coordinated bombings and shootings killed at least 185 people.
But they have in recent months expanded the targets down to the centre of the country, where Nigeria's beleaguered capital is located.
Abuja residents and foreigners who visit regularly have since learned to live with security checks and queues of cars waiting to be searched at prominent spots.
Boko Haram has claimed attacks that have killed more than 1,000 people in Nigeria since mid-2009.