Islamic State militants have accepted a pledge of allegiance by the Nigerian-grown Boko Haram extremist group, a spokesman for IS has said.

Nigeria’s home-grown Boko Haram group, newly weakened by a multinational force that has dislodged it from a score of north-eastern towns, has reportedly pledged formal allegiance to the Islamic State group.

Fighters from Nigeria’s Boko Haram militant group have seized Gwoza town, overwhelming soldiers based in the north-east area before attacking civilians, according to security officials and a witness.

Boko Haram militants dressed as soldiers slaughtered at least 200 civilians in three villages in north-eastern Nigeria and the military failed to intervene even though it was warned that an attack was imminent, witnesses said.

Suspected Boko Haram gunmen kidnapped eight girls from a village near one of their strongholds in northeastern Nigeria overnight, police and residents said yesterday.