KANO, Nigeria (AFP) - A girl thought to be as young as seven years old was killed along five others in a bombing in northeast Nigeria on Sunday as President Goodluck Jonathan conceded his government had underrated the capacity of the Islamist extremist group Boko Haram.
The attack on a market in the city of Potiskum is the latest in a string of such strikes in which children have been used.
Previous attacks have been blamed on Boko Haram.
Nineteen people were injured in the blast in Yobe state's commercial capital, a local vigilante leader said. "So far, five people were killed with the girl while 19 others have been taken to hospital for injuries," Buba Lawan said.
A hospital source speaking on condition of anonymity confirmed the dead and the wounded count.
The bombing highlights the severe security challenges facing Nigeria in the run up to March 28 presidential and parliamentary elections.
During a swing through neighbouring Chad, Cameroon and Niger, French Foreign Minister Laurent Fabius on Sunday urged Nigeria to entirely commit itself to battling Boko Haram.
"It is necessary that there be full commitment from Nigeria in the fight against Boko Haram," he told reporters during a press conference in Niger's capital, Niamey.
On Saturday in the Chadian capital N'Djamena, Fabius visited a coordination cell set up on a French military base between Cameroon, Chad, Niger and France.
Paris has promised to increase intelligence-sharing and other assistance to the armies of Nigeria and its three neighbours, which banded together to battle Boko Haram after the extremists expanded their campaign of across the region's borders.
President Goodluck Jonathan, who has been in office since 2011, is in a tough re-election campaign against ex-military ruler Muhammadu Buhari.
Voting initially scheduled for February 14 has been delayed for six weeks to give Nigeria's military time to secure the country, despite it's failure beat Boko Haram back during its six years of rampaging.
Jonathan admitted in an interview published on Sunday that he had earlier underestimated the Islamists, who have overrun swathes of the northeast.
"Probably at the beginning, we, and I mean myself and the team, we underrated the capacity of Boko Haram," Jonathan said in an interview with newspaper ThisDay.
He said that the military has recently acquired more arms and ammunition to battle the Islamists, and vowed their defeat was imminent.
Sunday's bombing in Potiskum was the second suicide attack in or near the market where new and second-hand phones are sold and repaired.
The first attack occurred on Jan 11, when two bombers - one of whom appeared to be around 15 - were blown up outside the market killing six people and injuring 37 others.
Before Sunday's strike, suspicious security guards and vigilantes said they tried to prevent the girl - who witnesses said appeared around seven - from entering the market.
"We sent her back four times, because given her age, she did not have anything to do in the market," Lawan said.
"When we were screening people, she bent and tried to pass under the ropes, some distance from our view. That was when the explosives went off."
In a sign of the distrust generated by the bombing campaign, Lawan said "we have barred women from entering the market to prevent further attacks".
More than13,000 have been killed while more than one million people have been left homeless since 2009 as the rebels try to carve out an Islamic state in Nigeria's northeast.