An “intelligence report” showed that Abubakar Shekau, the leader of the Boko Haram group, may have died between 25 July and 3 August, Lt-Col Sagir Musa said.
However, Boko Haram has not commented on the statement.
The intelligence report suggested that Shekau was shot on 30 June, when soldiers raided a Boko Haram base at Sambisa Forest in north-eastern Nigeria.
“Shekau was mortally wounded in the encounter and was sneaked into Amitchide, a border community in Cameroon for treatment.
“It is greatly believed that Shekau might have died between 25 July to 3 August 2013,” Col Musa said.
Lt-Col Musa added that a video of Shekau, released on 13 August, was “dramatised by an imposter to hoodwink the sect members to continue with the terrorism.”
Similarly, on 14 August, the military said it had killed Boko Haram’s second-in-command, Momodu Bama, also known by his alias “Abu Saad”. Correspondents say there is no independent confirmation of Shekau’s or Bama’s death.
The US in the past had put a bounty of $7m (£4.6m) on Shekau’s head but no ‘bounty hunter’ have come forward with undisputed evidence till date.