Jihadist extremist group Boko Haram has confirmed the death of its leader, Abubakar Shekau.

Confirming Shekau’s death in a short video sent to AFP, top Boko Haram commander Bakura Modu, also known as Sahaba, urged his faction’s commanders to remain loyal despite the loss of their historic commander.

In his video message relayed in Arabic, Sahaba called for revenge against the rival group Islamic State West Africa Province ISWAP which was born in 2016 from a split with Boko Haram. 

He also asked "Allah to bless the soul of Shekau" who died "as a martyr" and accused ISWAP leader "Abu Musab Al-Barnawi, that perverted aggressor" of killing him.

The announcement puts to rest the rumours that Shekau is still alive, albeit critically injured. 

Recall that Shekau is said to have died during infighting with a rival Islamic State-allied faction.

ISWAP commander Abu Musab Al-Barnawi had already claimed Shekau killed himself while on the run from ISWAP fighters.

With Shekau's death, ISWAP has established its status as the dominant force in the more than decade-long Islamist insurgency in the country's northeast.

Meanwhile, ISWAP fighters have taken over Shekau's stronghold in the Sambisa forest in their bid for consolidation, analysts and security sources have said.

But they say Barnawi would face potential resistance from hardline, pro-Shekau factions along Nigeria's border regions.