A US airstrike was carried out in Kabul on Sunday by the CIA, with President Joe Biden expected to give an address on a successful counter-terrorism operation at 12:30am UK time.
A senior official in his administration said: “Over the weekend, the United States conducted a counterterrorism operation against a significant Al Qaeda target in Afghanistan.
“The operation was successful and there were no civilian casualties.”
News of the strike was confirmed by Taliban spokesman Zabihullah Mujahid.
He condemned the actions of the US, calling it a “violation of international principles”.
The spokesman added: “Such actions are a repetition of the failed experiences of the past 20 years and are against the interests of the United States of America, Afghanistan and the region.”
The death of al-Zawahiri marks the biggest blow for the terrorist organisation since Osama bin Laden was killed in 2011.
The White House confirmed President Biden’s speech would take place on Twitter in a post which said: “Tonight at 7:30 PM ET, President Biden will deliver remarks on a successful counterterrorism operation.”
Al-Zawahiri, who was 71, was born in Egypt and trained as a doctor before he was imprisoned in 1981 for his involvement in the assassination of Egyptian President Anwar Sadat.
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At one point Al-Zawahiri narrowly escaped an American attack in the Tora Bora region of Afghanistan which reportedly killed his wife and children.
He made prolific appearances on extremist propaganda videos and audio tapes to encourage his followers to rise up against the West.
The US Government had offered a reward of up to $25million (£20.4million) for information leading to his capture.