Two girls were killed and three customs officers seriously wounded in a fresh blast in Nigeria's troubled northern city of Maiduguri, an army general said.
"Three customs officers were seriously injured in the attack while two child vendors - both of them girls - were killed in the blast," the commander of the city's joint task force, general Jack Okechukwu Nwobo, told AFP of Monday's attack.
Residents and witnesses put the death toll at about a dozen, however.
"I was about 100 metres (yards) from the customs bridge roundabout when the blast happened. It was a crowded area. I saw two vans conveying the dead. From my estimation, not less than 10 people were killed in the blast," said a resident near the scene.
Amnesty International condemned the attack.
"Several people were injured in a fresh bombing on Monday, also believed to have been carried out by Boko Haram,"the organisation said in a statement.
The exact nature of the blast was not immediately known. Security agents cordoned off the site of the explosion.
Nobody immediately claimed responsibility for the blast, which came less than 24 hours after suspected Islamists of the Boko Haram sect tossed bombs and fired on a crowded beer garden on Sunday, killing at least 25 people.
The National Emergency Management Agency said it was working with other rescue teams to evacuate the injured but gave no further details.
A violent streak
Boko Haram, which which demands the adoption of sharia law, or Islamic law, throughout Nigeria, claimed responsibility for a bomb blast 10 days ago outside the national police headquarters in the capital, Abuja. It is also believed to be behind a number of other attacks that killed more than a dozen people this month.
Reporting from Lagos, Al Jazeera’s Yvonne Ndege said: "A resident that we were able to get in touch with on the ground told Al Jazeera that they could hear the loud explosions and screams, cries of terror from people caught up in the chaos."
Quashing Boko Haram has now become a major priority for the government as it has replaced attacks on Nigeria's oil infrastructure the southern Niger Delta as the main security threat in Africa's most populous nation.
"There have been a series of meetings over the last week between Nigeria’s president, Goodluck Jonathan, and key security chiefs in Nigeria to figure out a strategy how exactly to get rid of Boko Haram," our correspondent said.
Maiduguri in Borno state is about 870km from Abuja and is considered a Boko Haram stronghold.
The group has been responsible for almost daily killings and attacks on police and government buildings in recent months in and around Maiduguri, which lies near Nigeria's borders with Chad, Cameroon and Niger.
It has vowed to keep killing people believed to support the establishment until sharia law is adopted, alongside other demands.
In a leaflet attributed to Boko Haram and distributed to journalists in Maiduguri recently, a man claiming to be a spokesman warned that the group would launch more attacks after being angered by comments from the national police chief.
Inspector-general of police Hafiz Ringim had said during a visit to the city that "the days of Boko Haram are numbered".
The alleged Boko Haram leaflet went on to warn residents of all northern states, including the district where Abuja is located, to stay indoors to avoid getting caught in the violence.
Nigeria, a nation of 150 million people, is divided between the Christian-dominated south and the Muslim-majority north. A dozen states across Nigeria's north already have sharia in place, though the area remains
under the control of secular state governments.
Boko Haram was thought to have been vanquished in 2009 after an uprising in which hundreds were killed. The military destroyed its main mosque and its leader, Mohammed Yusuf, died in police custody.
Jonathan, who was sworn in for his first full term in office a month ago, has voiced support for dialogue with Boko Haram.
But the group has an ill-defined command structure, a variety of people claiming to speak on its behalf, and an unknown number of followers. Some security analysts say its supporters number in the thousands.
Source: Al Jazeera and agencies