They have said that information provided by army officers has helped Boko Haram to ambush military convoys and attack barracks and outposts in its stronghold in north-eastern Nigeria.

The Afrika herald newspaper quoted an officer as saying that four other officers, in addition to the 15, were found guilty of “being disloyal and for working for the members of the sect”.

Ministry of Defence spokesman Major-General Chris Olukolade last week denied that senior military officers were being investigated for helping Boko Haram and sabotaging a year-old offensive to curb the five-year-old uprising that has killed thousands.

Boko Haram has attracted international condemnation and UN sanctions since its abduction in April of more than 300 schoolgirls, of whom 272 remain captive.