"We must now focus on moving the war to the heart of the homes and cities of the crusader West and specifically America," he said.
The Egyptian former doctor said Muslim youths should follow the example of the Tsarnaev and Kouachi brothers, who carried out the Boston marathon bombings and Charlie Hebdo shootings in Paris respectively.
The recording is thought to be around two months old, as it refers to former Taliban leader Mullah Omar as being alive. He was revealed to be dead in July.
His words come just days after another recording was released, claiming to be from al-Zawahiri, which dismissed the legitimacy of the so-called Islamic State.
"We don`t recognise this caliphate," he said
He added that IS had made "big mistakes" but hinted there may still be room for co-operation between the two groups, urging greater unity between militants.
Reference to events in that recording suggested it was probably made at least eight months ago.
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