Boko Haram fighters have massed in northeast Nigeria's Gwoza and killed several residents in the town considered to be the group's headquarters, a witness and a senator said Thursday.
Senator Ali Ndume told AFP he had received reports of the insurgent build-up in the town where Boko Haram last year had declared its caliphate.
Ndume and a woman who fled Gwoza on Tuesday said militant fighters had also killed several male residents.