Hundreds of people have been found dead in the northeast Nigerian town of Damasak, apparently victims of the Boko Haram insurgency, as details emerged on Monday of fresh attacks by the militants.

Reports of decomposing bodies littering the streets of Damasak came as president-elect Muhammadu Buhari denounced the Islamists as a bogus religious group and vowed to take a hard line against them when he comes to power at the end of May.

Northeast Nigeria had seen a lull in violence in recent weeks after a coalition of troops from Chad, Cameroon, Niger and Nigeria claimed major victories since February, reportedly flushing the militants out of areas they previously controlled.