A bomb strapped to a girl aged 'no older than 10' exploded in a busy market place in Nigeria, killing at least 20 people and injuring 18, security sources said.

The powerful explosion rocked the market in Maiduguri, which lies in the heartland of an insurgency by Sunni Muslim militant group Boko Haram, and was hit twice by female suicide bombers last year.

A Red Cross official said the blast split the young suicide bomber in two and flung one part across the road.

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.

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A bomb strapped to a girl aged 'no older than 10' exploded in a busy market place in Maiduguri, Nigeria, pictured is an explosion at the same market in July

Civilian vigilante Ashiru Mustapha said the explosives detonated as the girl was being searched at the entrance to the market.

'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.

'But sadly, the explosion went off before she was isolated, killing at least 10 people and injuring many others.'

The bomb went off at 12.15pm (11.15am GMT) today when the market was packed with traders.

The bodies of at least 16 bomb victims were counted in one hospital by mid-afternoon, civilian joint task force member Zakariya Mohammed told Reuters.

Boko Haram militants have increasingly used women and young girls as human bombs in their six-year quest for a hardline Islamic state, pictured is burnt Bama market destroyed by gunmen in April 2013

'Right now, there are 27 injured people in Borno Medical Hospital, while more were taken to other hospitals,' he said.

The market in the Borno state capital was cordoned off as health officials began the grim task of sifting through the wreckage and collecting body parts.

The northeast states of Borno, Yobe and Adamawa are bearing the brunt of a five-year-old insurgency by the Boko Haram, which wants to revive a medieval caliphate in Nigeria.

Last year more than 10,000 people died in the bloodshed.

Hours later, a suspicious vehicle that had been stopped at a checkpoint outside the city of Potiskum, in neighbouring Yobe, exploded at a police station as its driver was being taken in for questioning.

A police officer accompanying the car and the driver were killed, an officer said. Potiskum has been a repeated target for militant violence.

Both blasts came a week after a major Boko Haram attack on the fishing town of Baga in northern Borno State, which is believed to be the worst in the bloody six-year insurgency.

Zahra'u Babangida, 13, was arrested in December with explosives strapped to her body and told journalists that her parents volunteered her to take part in a suicide attack in Kano.

Boko Haram launched its first female suicide attack in June last year in the northern state of Gombe and there have been a spate of bombings since, including four in a week in the city of Kano in July.

The same month a 10-year-old girl was found in Katsina state wearing a suicide vest, prompting fears that young girls were being forced into becoming human bombs rather than through ideological motivation.

Forced conscription of young men and boys by Boko Haram has been well-documented. Last July, three women said to be 'female recruiters' for Boko Haram were arrested.

An alleged trainer of women bombers was also detained in Kano in August with up to 16 'trainees'.

On Friday, militants fought running battles with troops in the Yobe state capital, Damaturu, leading to the destruction of a mosque, shops and a market.