Militant Islamist group Boko Haram has torched several homes and a school during a raid on a town in north-eastern Nigeria, the army says.

The insurgents were heavily armed, storming the town of Korongilum on Tuesday evening in a convoy of trucks mounted with guns, as well as motorcycles.

Eyewitnesses said three people were killed and six others injured when the militants attacked residents as they were returning home from their farms.

The head of military operations in the north-east, Brig Gen Adesini Olusegun, confirmed the attack but declined to give details on casualties.

The militants caused global outrage in 2014 when they abducted more than 270 schoolgirls in nearby Chibok.