Two key branches of al-Qaida in Yemen and North Africa have called for jihadists in both Iraq and Syria to join together to fight the US-led coalition aimed at defeating Isis (now known as the Islamic State).

A joint statement was released by al-Qaida in the Arabian Peninsula (AQAP) and al-Qaida in the Islamic Maghreb (AQIM), which called upon their jihadist "brothers" in Iraq and Syria to "stop killing each other and unite against the American campaign and its evil coalition that threatens us all".

"Make the unity of the infidel nations against you a reason for your unity against them," the statement added.

It claimed that Washington was "leading a Crusader campaign against Islam and all Muslims."

Both branches are vehemently anti-Western but also rejected Islamic State's announcement of a "caliphate" and Abu Bakr al-Baghdadi as the "caliph" of all Muslims around the world.

The two cells of the terror group pledged their allegiance to Ayman al-Zawahiri, the successor to the group's former leader, Osama bin Laden, who was killed by US special forces in 2011.

AQAP, based in Yemen, have been able to smuggle three explosive devices on to US-bound flights but none of their aviation attacks have been successful.

The al-Qaida branch's bomb mastermind Ibrahim al-Asiri created the underwear bomb that a Nigerian man attempted but failed to detonate on a passenger jet in Detroit in December 2009.

The call to arms came as the US conducted its first air strike against IS in the revised strategy against the group as part of a broader international coalition.

US President Barack Obama last week detailed his plan to "degrade and ultimately destroy" the terror group as it continues to expand its "caliphate" straddling the Iraqi-Syrian border.