Sixteen people were killed and over 20 injured when a bomb strapped to a 10-year-old girl exploded in a busy market place in Nigeria's Maiduguri city on Saturday at 12.15 pm WAT (4.45 pm IST).

"The explosive devices were wrapped around her body and the girl looked no more than 10 years old," Reuters quoted a police source as saying. The injured were admitted to nearby hospitals.

No extremist or terrorist agency has so far claimed responsibility for the attack.

The city is the capital of northern Borno state and often targetted by the militant group Boko Haram. The group is seen as posing the biggest threat to Nigeria.

Civilian vigilante Ashiru Mustapha said the explosives detonated as the girl, who was oblivious to what was strapped on to her body, was being searched at the entrance to the market.

"...She was searched at the entrance of the market and the metal detector indicated that she was carrying something. But sadly, the explosion went off before she was isolated, killing at least 10 people and injuring many others," according to Mustapha, reports abcnews.

A Borno State police spokesman Gideon Jubrin said: "Casualty figure: 20 dead and 18 injured, including the female suicide bomber that detonated the improvised explosive device."

In an attack at the market on 1 December, over 10 people were killed and in an earlier attack in the previous week, over 45 people lost their lives.

In July, a 10-year-old girl in Katsina state was found wearing a suicide vest, prompting speculation that young girls were being forced into becoming human bombs.