NEW: Spokesman encourages potential fighters to go to Africa if they cannot get to Iraq or Syria
Abu Bakr al-Baghdadi's spokesman congratulated "our jihadi brothers" in western Africa
Boko Haram's leader had extended his pledge to be an ally in an audio message last week
In an audio message purportedly from an ISIS spokesman, the group announced that a pledge of allegiance from Nigerian-based Boko Haram has been accepted by ISIS leader Abu Bakr al-Baghdadi.
ISIS supporters posted the audio online. CNN cannot independently verify the 28-minute message.
The message says that ISIS, which calls itself the Islamic State, has expanded to western Africa and congratulated “our jihadi brothers” there.
An ISIS spokesman encouraged people to join fighters in Africa if they cannot make it to Iraq or Syria.
Boko Haram’s leader, Abubakar Shekau, announced in an audio message last week that his terror group wanted to join ISIS.
Jacob Zenn, a terror expert who lives in Nigeria, told CNN on Saturday the alliance would make sense for both groups.
“Boko Haram will get legitimacy, which will help its recruiting, funding and logistics as it expands,” Zenn said. “It will also get guidance from ISIS in media warfare and propaganda. Previously Boko Haram was a sort of outcast in the global Jihadi community. Now it is perhaps ISIS’s biggest affiliate.
“ISIS gets more international legitimacy as a global caliphate.”
Years of terror
Boko Haram, whose name translates as “Western education is sin,” has been waging a yearslong campaign of terror aimed at instituting its extreme version of Sharia law.
Boko Haram has terrorized northern Nigeria regularly since 2009, attacking police, schools, churches, mosques and civilians. It has also kidnapped students, including more than 200 schoolgirls who were abducted in April and remain missing.
Much of this violence has taken place in Nigeria. But neighboring countries, such as Cameroon and Chad, have also been hit increasingly hard.
CNN’s Paul Cruickshank contributed to this report.