A split has reportedly emerged among one of the most deadly Islamist groups in the world.

Boko Haram has been responsible for numerous atrocities in several African countries - including the mass kidnap of Nigerian schoolgirls.

Reports suggest that ISIS wanted Boko Haram to replace its leader, Abubakar Shekau, but after he refused to step down, two factions have emerged.

His rival, Abu Musab al-Barnawi has been declared the leader via publications linked to ISIS.

Boko Haram has fought a long war with the Nigerian army and is thought to have killed up to 17,000 people, many of them Christians.

AP reports that al-Barnawi has claimed Boko Haram will continue to bomb churches and kill Christians.

Boko Haram pledged allegiance to ISIS in March 2015. It was reported last year that Boko Haram's attacks have actually been more deadly than ISIS'. As well as the Nigerian Army, which has fought Boko Haram since 2009, the US has placed a bounty on the heads of Boko Haram leaders.

The BBC reports that, "Abubakar Shekau's outburst clearly shows that there are deep disagreements, which could translate into clashes between the foot soldiers loyal to the two leaders... But some security analysts caution that the internal wrangling could make it more deadly and unpredictable."