In what appears to be matter of turf war between the world's most dangerous terrorist organisations, al Qaeda leader Ayman al-Zawahiri has openly opposed Islamic State and its activities in a recently released audio message.

The Egyptian who is a doctor by profession has accused ISIS top leader Abu Bakr al-Baghdadi of 'sedition' and has insisted that Baghdadi is not the leader of all Muslims and militant jihad as 'caliph' of the Islamic State. Baghdadi had claimed thus 14 months ago in a Mosul mosque.

A file photo of Abu Bakr al-Baghdadi at his first public appearance in a mosque in Mosul, Iraq | Source: Reuters

He has previously maintained that Qaeda will fight alongside ISIS in combating the West. "Despite the big mistakes (of Islamic State), if I were in Iraq or Syria I would cooperate with them in killing the crusaders and secularists and Shiites even though I don't recognize the legitimacy of their state, because the matter is bigger than that," he said as reported by the Huffington Post .

Al Qaeda expert Will McCants of the Brookings Institution told Daily Mail that Zawahiri neither recognises ISIS as a caliphate nor Baghdadi as a caliph.

"However, it is an emirate and if he were in Iraq and Syria, he would fight alongside it. That seems like a bit of an olive branch," he added . He further warned that if the two organisations unite all efforts to stabilise the crisis in Middle East will turn catastrophic.

A file photo of Ayman al-Zawahiri (right) with Osama Bin Laden. | Source: Wikipedia

ABC News reports that former Director of the US based National Counterterrorism Center, Matthew Olsen echoed the same concerns and said that if the unification of the two forces would be terrible. However, he also conveyed that the possibility of pitting the two against each other might prove beneficial for United States' counter-terrorism operatives.

Zawahiri, who carries a US bounty of $25 million on his head assumed leadership of al Qaeda in June 2011 after US forces killed Osama bin Laden in Pakistan. Accusing Baghdadi of sedition is an about turn from the olive branch earlier offered.