The leader of al-Qaeda has attacked Isis for “madness” and “exceeding the limits of extremism” as the two terror groups continue to compete for territory and supporters around the world.

Ayman al-Zawahiri, who succeeded Osama bin Laden when he was killed in 2011, criticised Isis for killing and “slandering” his own jihadis.

In an audio message, he branded the rival group’s members “cowards” and liars with a “thirsty desire for authority”.

“Isis was struck with madness in takfir [declaring other Muslims to be apostates] and exceeded the limits of extremism,” al-Zawahiri said.

“They make takfir on the basis of lies, fabrications and even good deeds of obedience…[it is] is political, convenient and opportunistic.”

The extremist, who has had a $25m (£20m) bounty on his head since 9/11 and is under global sanctions due to his links to global terror attacks dating back to the 1990s, claimed Isis was “misusing the enthusiasm of the youth”.

His message was issued as an audio file in Arabic, being distributed on al-Qaeda channels and then translated and spread by supporters on social media.