The leader of al-Qaeda has urged warring fighters in Syria to unite or risk death while criticizing again the Islamic State (IS) group in an audio recording, Al Jazeera reported.
In the clip, posted online on Sunday, Ayman al-Zawahiri criticized the UN-backed political process to find a solution in Syria and praised al-Nusra Front, an al-Qaeda offshoot which controls most of Idlib province.
"We have to want the unity of the Mujahideen in Sham [Syria] so it will be liberated from the Russians and Western Crusaders. My brothers ... the matter of unity is a matter of life or death for you," Zawahiri says.
Al-Nusra Front is part of an alliance of armed groups known as Jaish al-Fatah, which is leading battles against Syrian President Bashar al-Assad's forces and his Russian- and Iranian-backed allies in the southern Aleppo countryside.
n January, al-Nusra Front tried unsuccessfully to convince rival Sunni factions - including the powerful Ahrar al-Sham - to merge into one unit.
As successor to Osama bin Laden, Zawahiri has the allegiance of al-Qaeda branches in the Middle East, North Africa and South Asia.
The authenticity of the recording, the first since January, could not be immediately verified, but it had the hallmarks of previous Zawahiri tapes.
He is believed to be hiding in a border area between Afghanistan and Pakistan.
In the audio clip, Zawahiri emphasised once again the ideological divide between al-Qaeda and IS.
He described IS as "extremists and renegades" whose followers would eventually disavow their beliefs and methods.
Al-Qaeda's dominance is being challenged by IS, which controls territory in Syria and Iraq and has branches in Libya and Yemen.