ABUJA (AFP) - Nigeria's military on Sunday rejected a claim by Boko Haram's leader that a north-east town seized by the insurgents earlier this month has been placed under an Islamic caliphate.

"That claim is empty," defence spokesman Chris Olukolade said in reference to Abubakar Shekau's boastings about the town of Gwoza in Borno state.

"The sovereignty and territorial integrity of the Nigerian state is still intact," and operations "to secure that area from the activities of the bandits is still ongoing," he added.