News, views and top stories in your inbox. Don't miss our must-read newsletter Sign up Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

Terror group al Qaeda has 'declared war' on fellow jihadists Islamic State in an angry speech by its leader.

Ayman al-Zawahiri, who replaced Osama bin Laden four years ago, blasted his opposite number in an audio message on the eve of the 9/11 anniversary.

Al-Zawahiri accused the ISIS chief Abu Bakr al-Baghdadi of 'sedition' for last year declaring he is the leader of all Muslims - the fourth Caliph.

(Image: Getty)

In the message, released online on Wednesday, Egyptian doctor al-Zawahiri said: “We have endured a lot of harm from Abu Bakr al-Baghdadi and his brothers, and we preferred to respond with as little as possible, out of our concern to extinguish the fire of sedition.

“But Abu Bakr al-Baghdadi and his brothers did not leave us a choice, for they have demanded that all the mujahideen reject their confirmed pledges of allegiance, and to pledge allegiance to them for what they claim of a caliphate."

Al-Baghdadi had called on the world’s Muslims to “obey” him as the head of the caliphate in a rare public speech in Mosul, Iraq last year.

He said: "I am the wali (leader) who presides over you, though I am not the best of you, so if you see that I am right, assist me.

“If you see that I am wrong, advise me and put me on the right track, and obey me as long as I obey God in you.”

Zawahiri said "everyone was surprised" by al-Baghdadi's declaration and he had done this "without consulting the Muslims".

Video Loading Video Unavailable Click to play Tap to play The video will start in 8 Cancel Play now

A counter terrorism expert has said the move will 'irreconcilably' divide the two militant groups.

Speaking to 6abc, Matthew Olsen added: "Zawahiri until now has not been willing to openly condemn Baghdadi and ISIS - it highlights how deep the division is between al Qaeda leadership and ISIS.

"It suggests that the differences are irreconcilable.

"Had ISIS and al Qaeda realigned by joining forces, it would be terrible."

The outburst came just ahead of the 14th anniversary of the September 11 attacks.

It is hoped the division could provide an opening for counter-terrorism operatives to exploit.

Read More: ISIS blow up 2 men with dynamite after forcing them to watch burning fuse

Mr Olsen said misinformation tactics could pit the two jihadi menaces against each other.

ISIS was formerly the al Qaeda branch in Iraq but split from the larger group two years ago.

In Afghanistan and Pakistan, ISIS "has been fighting non-stop" with the Taliban and al Qaeda, an official said.

They have also sometimes fought each other in Syria too.