Boko Haram and the Islamic State group, two terrorist organizations who have been aligned since 2015, may be at war with one another.

Earlier this month, ISIS — a terrorist group that operates primarily out of Syria but has several affiliated operations throughout the Middle East and Africa — named a new leader for Boko Haram, replacing Abubakar Shekau, who was at the helm when the group pledged allegiance to the foreign group last year. The coronation quickly created a rift in the Nigerian terror group, leading to bloody clashes between supporters of both leaders that have killed at least a handful of militants.

ISIS named the new leader, Abu Musab al-Barnawi, in one of the most recent editions of the purported ISIS news outlet Al-Naba. There was no mention at the time of Shekau or what had happened to him (some reports began to surface that he had perhaps been killed but more recent videos have since seemed to prove that he is alive), leading to the distrust within Boko Haram’s army.

Boko Haram became well known internationally after it began its armed insurgency in northeast Nigeria in 2009. Their operations have led to the deaths of tens of thousands of people and the displacement of more than 2 million more people from the area. While their operations have remained largely in the northeast of the country, they have branched out and began attacking other areas including parts of Cameroon, Chad and Niger.

Shekau was the second commander of the group and took control after the founding leader, Nigerian cleric Mohammed Yusuf, died in police custody soon after the group was founded.

Boko Haram’s connection to ISIS has been disputed, however. Though allegiance was pledged and the group is referred to as the West African branch of the Syrian caliphate,  U.S. military sources have indicated that the groups have always had a fractured relationship.