In the roughly six-minute video, five unmasked men of Somali ethnicity arrive in large, new-looking SUVs. They are carrying weapons and surrounded by heavily armed bodyguards.
Speaking in Arabic under palm trees, the men take turns imploring Somalis and members of the insurgent group Al-Shabaab, whom they refer to as ''truthful mujahedeen" to join their movement to fight the West, and to pledge allegiance to ISIS.
This is the first time ISIS has appealed directly through video to Al-Shabaab to merge with them.
Al-Shabaab, meaning "the youth," is a Somalia-based insurgent group that formally pledged allegiance to international terror organization al Qaeda in 2012.
However, there has been a strong international effort to counter it, including military action by U.N.- and U.S.-backed African Union forces.
Since 2011, when the militants were forced out of Mogadishu, the capital, the group has been weakened significantly. It has lost territory and revenue from being pushed out of key seaports. One of the most major blows came in 2014 when its leader, Ahmed Godane, was killed in a U.S. drone strike.
However, in what some experts see as desperate attempts to appear formidable, the militants have launched deadly attacks both inside Somalia and neighboring countries, including two massive assaults in Kenya: the killing of 142 students at a university
and the 2013 shopping mall attack in Nairobi
that left more than 67 dead.
Expert: Merger would be 'significant ideological victory'
Security expert Ryan Cummings says that ISIS' desire to merge with Al-Shabaab is part of its international expansion plan.
"Al-Shabaab is the largest jihadi movement in East Africa, and central to the core mandate of ISIS is the unification of the Muslim world, so it would be a significant ideological victory for the group. It would be massive from a public relations perspective, which is central to the Islamic State's operations," Cummings told CNN.
"This is all part of the ongoing attempts by the Islamic State to try to coax Shabaab into pledging its allegience. As we know, Al-Shabaab currently serves as an al Qaeda franchise. The issue is obviously that the Islamic State still wants to create the perception that it's growing and branching out to various parts of the world. The only way that it will be able to achieve this will be to have groups serving as an extension in their various areas of operation," he added.
ISIS has already merged with several jihadi groups across the continent once loyal to al Qaeda. Its most recent coup was in West Africa, as Boko Haram declared its "bayat," or pledge, to join ISIS earlier this year. At the time, Boko Haram consisted of roughly 6,000 fighters and controlled up to 20,000 square kilometers (7,700 square miles, roughly the size of Massachusetts) of northeastern Nigeria.
Experts see friction within Al-Shabaab leadership
In most of these countries, the militant groups are seeking to topple the secular governments and to replace them with Islamic caliphates instituting Sharia law. Experts say ISIS supports these domestic ambitions, which Al-Shabaab subscribes to as well.
With a possible merger, experts warn, there's a risk of more frequent brutal attacks as Al-Shabaab seeks to expand its operational and recruitment reach farther into Kenya, Tanzania and even Uganda.
Al-Shabaab is currently seen as a predominantly Somali militant group, and has been attempting to recruit elsewhere in East Africa. A partnership with ISIS, experts say, will increase its cosmopolitan appeal, which could potentially increase recruitment.
However, sources familiar with Al-Shabaab's internal affairs say that there is currently friction within the leadership of the group, between those who want to maintain and even increase relationships with global jihad movements, and those who want to stick to their initial domestic mandate.