Five children, four girls and one boy, were behind a series of blasts in the north-eastern Nigerian city of Maiduguri on Thursday, sources say.

Fifteen people, including the bombers, died and more than 35 were injured in the attacks at a mosque and house of vigilante leader, they said.

More than 100 people died in similar attacks in the city two weeks ago.

Maiduguri is where Boko Haram Islamist militants were first based when they began their insurgency six years ago.

Some 17,000 people are said to have been killed in that time and attacks by the group have intensified since Muhammadu Buhari became president in May, vowing to defeat the insurgents.