The Nigerian terror group Boko Haram has pledged allegiance to ISIS, according to an audio message thought to be made by its leader, Abubakar Shekau. In the message, the Boko Haram leader said: "We announce our allegiance to the caliph... and will hear and obey in times of difficulty and prosperity. We call on Muslims everywhere to pledge allegiance to the caliph."

The message was posted online on Saturday, and while its authenticity has not been confirmed, many experts believe that the audio in question is genuine. ISIS has yet to respond to the audio.

According to Jamestown Foundation Terrorism expert Jacob Zenn, both groups have much to gain from a potential pairing up. Boko Haram will gain legitimacy that it has long argued for, something that will help it recruit and fund further expansion into West Africa. Meanwhile, ISIS will gain greater acceptance as an international network. The organization aims to set up a global caliphate that would be governed by its rigid interpretation of Shariah law.

This is not the first time the Nigerian terrorist network has voiced support for ISIS. Last year, Shekau declared a Nigerian town under his control as part of the caliphate, a word used by ISIS to describe parts of Iraq and Syria that it controls. ISIS has not openly acknowledged Boko Haram, but there have been references to Nigerian jihadists in a few of its videos.

U.S. intelligence has said it is unlikely that the two groups will be able to foster cooperation, since even though they base themselves on similar extreme interpretations of Islam; Boko Haram has its practices rooted in African culture, whereas ISIS has expressed racist views towards blacks in the past.

Boko Haram, which literally means "Western education is a sin" has been responsible for a number of deadly attacks in the West African country. In recent years, it has raided countless villages, detonated bombs in crowded marketplaces and conducted mass kidnappings across the country. The organization received international condemnation following its raid and kidnapping of 276 female students from a government secondary school in Chibok.