The Nigerian military announced Thursday that the leader of West Africa’s top Islamic State-linked extremist group is dead.

Details of Abu Musab Al-Barnawi’s death have yet to be confirmed as the Nigerian military has not disclosed how they have come across the knowledge of his death. The Islamic State group has also not commented on the event.

“I can authoritatively confirm to you that Abu Musab is dead. As simple as that. He is dead and remains dead," Chief of Defence Staff General Lucky Irabor told reporters.

Al-Barnawi was the eldest son of Boko Haram founding leader Mohammed Yusuf. Boko Haram is a Nigeria-based terrorist group with a presence in Chad, Niger and northern Cameroon, and has carried out an Islamist uprising for over a decade.

Under al-Barnawi leadership, the Islamic State West Africa Province (ISWAP) have shifted their focus to targeting the Nigerian military and its allies. The International Crisis Group estimated that the group has up to 5,000 fighters that overshadow the almost 2,000 in the Shekau-led faction.

The United Nations reported that ISWAP actions in Nigeria have led to more than 36,000 deaths and has displaced over 1.9 million people due to violence. More than 80% of those displaced are women and children.