The Islamic State West African Province (ISWAP) militant group said in an audio recording on Sunday that Abubakar Shekau, leader of rival Nigerian militant Islamist group Boko Haram, was dead.

Shekau died around May 18 after detonating an explosive device when he was pursued by ISWAP fighters following a battle, a person purporting to be ISWAP leader Abu Musab al-Barnawi said on the audio recording.

“Abubakar Shekau, God has judged him by sending him to heaven,” he can be heard saying.

Last month, Nigeria’s military said it was investigating Shekau’s alleged death, also reported in Nigerian and foreign news outlets. The audio statement is ISWAP’s first confirmation that its arch rival in the Lake Chad region has been killed.

Shekau’s death could lead to the end of a violent rivalry between the two groups, enabling Islamic State West Africa Province (ISWAP) to absorb Boko Haram fighters and consolidate its hold on territory in northeastern Nigeria, political analysts said.