IS group accepts allegiance pledge made by Nigeria’s Boko Haram

“Our caliph, God save him, has accepted the pledge of loyalty of our brothers of Boko Haram so we congratulate Muslims and our jihadi brothers in West Africa,” Abu Mohammad al-Adnani said, referring to IS group leader Abu Bakr al-Baghdadi.

He also called on Muslims who could not join the fight in Syria and Iraq to instead enter combat in Africa.

Since its advance in June, the IS group now controls large swaths of Iraq and Syria where it has declared an Islamic "caliphate". It has previously drawn expressions of allegiance by jihadists in Egypt and Libya.

On Saturday, an audiotape attributed to Boko Haram leader Abubakar Shekau said "we announce our allegiance to the Caliph of the Muslims, Ibrahim ibn Awad ibn Ibrahim al-Husseini al-Qurashi," referring to IS leader Abu Bakr al-Baghdadi.

Shekau has previously mentioned Baghdadi in video messages but has up until now stopped short of pledging formal allegiance.

But there have been increasing signs that the Nigerian militants, whose six-year insurgency has claimed more than 13,000 lives and left 1.5 million people homeless, have been seeking a closer tie-up.

IS spokesman Adnani insisted that the caliphate was growing.

"Our caliphate is resisting and it is advancing in the right direction. We are fighting the Crusaders and the rafidah (Shiites) and day by day the Islamic State is becoming strong," he said.

He insisted that the jihadist group is "sure of its victory" regardless of the challenges it is facing.

For months, the IS group has been targeted with air strikes from a coalition led by the United States and suffered territorial setbacks in Syria and Iraq.

And Iraqi government forces have closed on the city of Tikrit this week in a bid to retake it from the group.

(FRANCE 24 with AFP, REUTERS)