The Islamic State militant group, which controls parts of Syria and Iraq, has accepted a pledge of allegiance from the Nigeria-based Boko Haram extremist organization.
In an audio statement Thursday, an Islamic State spokesman welcomed what he called the expansion of the group's self-declared Islamic caliphate to West Africa.
"The caliph, may God protect him, has accepted the sworn allegiance of the Sunni brothers' call for the jihad. We congratulate our Muslim and mujahedeen brothers in West Africa for their allegiance," said Abu Mohammed al-Adnani.
Boko Haram leader Abubakar Shekau last week pledged in a video that his group will "hear and obey" Islamic State leader Abu Bakr al-Baghdadi.
The extent to which the two groups may be coordinating their efforts is not clear.
Others claim allegiance
Several other Islamic insurgent groups around the world have also claimed allegiance with the Islamic State group, though in most cases the union appears to be symbolic.
Earlier this week, Nigerian President Goodluck Jonathan told VOA that Boko Haram fighters are being trained at camps in the Middle East run by Islamic State militants.
"We know the links are there," Jonathan said, adding that some Boko Haram members have gone to train at Islamic State-run camps and have since returned.
He refused to mention specific countries when asked about the location of the reported camps.
Both groups, which follow their own strict interpretation of the Quran, are under pressure as a result of military strikes launched by separate multinational coalitions.
Jonathan predicted his coalition – which includes Chad, Niger and Cameroon – will oust Boko Haram from the territory it controls in northeastern Nigeria within the next three weeks.
The Islamic State group has come under fire from airstrikes by a U.S.-led coalition in Iraq and Syria. The Islamic State has begun to lose ground to Iraqi forces, who are carrying out an offensive to retake former leader Saddam Hussein's hometown of Tikrit.
But al-Adnani, the Islamic State spokesman, on Thursday played down those advances, saying any victories the "crusaders and rejectionists speak about are exaggerated, delusional and fake."