In the 50-minute tape of a meeting with the inner circle of his militant Islamist group obtained by AFP , Shekau said he killed “Tasiu” — also known as Abu Zinnira over an apparent plot to oust him
AFP claim they received a copy of the recording earlier this month and the tape appears to have been meant for circulation only within the armed Islamist movement.
“You should hear me: I killed Tasiu, hear me well,” he told the gathering in Hausa
Shekau states the date of the meeting — December 18 — and said it had been called to discuss “those elements grumbling over the killing of Tasiu”.
Shekau has been the most visible face of Boko Haram over the years, claiming attacks and launching rambling but Abu Zinnira has acted on occasion as de facto spokesman and appeared in video recordings, including those about the more than 200 schoolgirls kidnapped from the town of Chibok in April 2014.
In one video released in August last year, Abu Zinnira warned that the remaining girls still being held would die if troops attempted to rescue them.
In the December audio recording, Shekau accused Abu Zinnira of plotting with another senior commander called Baba Ammar to take over leadership of the group.
He accused them of sending fighters to carry out raids without his consent, spreading rumours among his lieutenants that he intended to kill them and portraying him as unfit to lead.
“Tell me, what is the punishment… for the people that plot against their leader?” he asked.
“By our code of allegiance we don't hesitate to pass appropriate sanction on any one of us that commit an offence.”
Last August, the Islamic State group announced that Abu Musab Al-Barnawi was now Boko Haram's leader.
Barnawi's is the son of Mohammed Yusuf, who founded Boko Haram in 2002. He was killed in police custody in 2009, after which Shekau — his deputy — took over.
Followers of the two factions have reportedly clashed while Barnawi has blamed Shekau's high-handed leadership style and his indiscriminate killings of his lieutenants for the split.
Shekau in the recording denounced his detractors as divisive influences.
“Devil's advocates are at work, trying to instill doubt in the minds of our fighters after realising we are gathering momentum for real jihad,” he said.
“They try to confuse whoever they see getting close to me and distance him from me, they are going about dampening the spirit of our fighters.
Boko Haram insurgency has killed at least 20,000 in northeast Nigeria since 2009 and left 2.6 million homeless.