Witnesses and hospital sources said a total of six people were killed after she triggered the explosive devise in a market in the northeastern city of Potiskum on Sunday.

"(She) refused to be checked at the gate to the market and an argument ensued," witness Ibrahim Maishago told the Reuters news agency by telephone. "She let off the bomb, killing herself and five others, while many were injured."

The AFP news agency cited a local vigilante leader, who said that in addition to the six killed, 19 others had been rushed to hospital suffering from varying degrees of injury.

Both wire services cited witnesses who said the girl appeared to be only 7 or 8 years old.

There was no immediate claim of responsibility for the bombing, but since last year, the Islamist militant group Boko Haram has been known to use female and child suicide bombers to carry out attacks.

This was the second such attack to hit the market in Potiskum, the commercial capital of Nigeria's Yobe state, after a previous one last month, which killed six people and injured more than 30 others. That was a dual suicide attack, in which one of the bombers appeared to be around 15 years old.

President 'underrated' Boko Haram

President Goodluck Jonathan, who is running for another term when Nigerians go to the polls in presidential and parliamentary elections next month, has been criticized for not taking tougher action against Boko Haram earlier than he did. In a newspaper interview published in the ThisDay newspaper on Sunday, the president conceded that he had initially underestimated the Islamists.

"Probably at the beginning, we - and I mean myself and the team - we underrated the capacity of Boko Haram," Jonathan said.

Recently, though, the military appears to have been upping its fight against Boko Haram, with Nigerian forces having claimed on Saturday that they had retaken the northeastern border town of Baga from the Islamists.

pfd/gsw (Reuters, AFP)