Suicide bombers have hit the north-eastern Nigerian town of Chibok during market day, killing at least 13 people, reports said.

At least three attackers were involved, some of them female, witnesses said. More than 30 people were injured.

It is not yet known who was behind the attack.

But suspicion is likely to fall on militants from the Boko Haram Islamist group, who abducted more than 200 schoolgirls from Chibok in 2014.

A town elder warned that the death toll could rise.

"The situation is now tense and there's so much confusion. It will take some time before we can be able to have a clearer picture of the casualties," Ayuba Chibok told the AFP news agency.

'In shock'

One of the attackers struck at a security checkpoint, while another managed to reach the busy market. A third was identified by residents before detonating explosives close to the market, the reports said.

"People I spoke to are in shock, some of them are still crying," a former town resident Malam Ayouba told the BBC Hausa service.

On Monday at least 25 people died in suicide bombings in the northern Cameroonian town of Bodo.

Earlier this month, Nigeria's President Muhammadu Buhari ordered a new investigation into the kidnapping of more than 200 schoolgirls from Chibok by Boko Haram.

The militants stormed a boarding school, abducting the girls from their dormitories.

Although the Nigerian military has freed hundreds of people held by Boko Haram in recent months, they did not include any of the Chibok girls.