Gunmen had invaded the school premises last Friday and abducted over 300 students after a gun duel with the police.
The leader of the terror group, Abubakar Shekau, later released a video claiming responsibility for the dastardly act.
The Defence Headquarters has, however, discredited the claim, insisting the act was carried out by bandits.
The one-minute long video features speeches from Shekau and a teenager believed to be one of the abducted schoolboys.
Scores of other young boys could be seen behind him, all covered in dust and appearing to be within a forest area.
Watch the video below;