The powerful explosion rocked the city's Monday market at about 12:40 pm (1140 GMT) when it was packed with shoppers and traders. The same market was hit twice by female suicide bombers late last year.
There was no immediate claim of responsibility but Boko Haram militants have increasingly used women and young girls as human bombs in their six-year quest for a hardline Islamic state.
"The girl was about 10 years old and I doubt much if she actually knew what was strapped to her body," he told AFP.
"In fact, she was searched at the entrance of the market and the metal detector indicated that she was carrying something.
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"But sadly, the explosion went off before she was isolated, killing at least 10 people and injuring many others."
The market was cordoned off as health officials began the grim task of sifting through the wreckage and collecting body parts.
He added: "Many people sustained life-threatening injuries."
Witness Abubakar Bakura said: "The blast split the suicide bomber into two and flung one part across the road.
"Among the dead are two vigilantes who were searching the girl. I am pretty sure the bomb was remotely controlled."
An attack at the market on December 1 killed more than 10 people, and the previous week more than 45 people lost their lives in an attack there.
In July, a 10-year-old girl was found in Katsina state wearing a suicide vest, prompting speculation that young girls were being forced into becoming human bombs rather than through ideological motivation.