As if Islamic State was not enough to cash in on the vulnerability of young minds and provoke them to carry out killings, now al Qaeda chief Ayman al-Zawahri has issued a call to the Muslims, egging them on to stage lone-wolf attacks in the USA and other western countries.

“We should now concentrate on shifting the conflict to the guts of the houses and cities of the crusader West and particularly America”, he stated in an audio recording posted on-line on Sunday, referring to nations making up the Western-led coalition in Iraq and Syria.

He suggested for the Muslim youth to take after Dzhokhar Tsarnaev, the Boston Marathon bomber; and the Kouachi Brothers responsible for the Charlie Hebdo shootings in Paris. He views the group as illegitimate, but has also urged unity, saying he would join them in the common cause of fighting Western and secular forces in Iraq and Syria.

It was not clear when the Al-Zawahiri audio recording was made but references to former Taliban leader Mullah Mohamed Omar as being alive suggest it is at least two months old. Omar’s demise was introduced by Afghanistan’s authorities in late July.

He called for the formation of an independent sharia court to settle any disputes between terrorists.

Also in the recording, al-Zawahri took a stab at ISIS leader Abu Bakr al-Baghdadi.

Al-Qaeda’s Syria affiliate, Al-Nusra Front, allied with other Islamist rebel groups, has been locked in deadly clashes with IS for control of territory in the north and around Damascus.

Al-Zawahiri, who has a £16million USA bounty on his capture, added that “everyone was surprised” that Baghdadi appointed himself as the leader of a caliphate “without consulting the Muslims”.