Ayman Al Zawahiri, a feature on the US's most wanted terrorist list, has been killed by a US drone in Afghanistan.
After the September 11 attacks, the US State Department offered a reward of up to $25 million for information leading directly to the apprehension and conviction of Al Zawahiri.
He is believed to have been involved in some of Al Qaeda's biggest terrorist operations, helping to organise the 2001 attacks, when airliners hijacked by his group Al Qaeda were used to kill 3,000 people in the US.
There, he was charged for his role in the August 7, 1998, bombings of the US embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya.
US President Joe Biden revealed on Monday that he authorised a precision strike in the Afghan capital, Kabul, to kill Al Zawahiri with two Hellfire missiles.
The drone strike on Saturday was approved after weeks of meetings with advisers, according to American officials.
Eleven years after the killing of his counterpart and close friend Osama bin Laden in neighbouring Pakistan, Al Zawahiri has become the public face and voice of the terrorist group in many recordings.
A videotape aired by Al Jazeera network in 2003 showed Al Zawahiri and bin Laden walking on a mountainside.
Who was Ayman Al Zawahiri?
Born in the Egyptian city of Giza in 1951, Al Zawahiri had just turned 71 when he was killed during a visit with relatives, according to the US president.
His killing came one year after the US withdrew its troops from Afghanistan and brought an end to a 20-year occupation.
He came from a well-to-do family of physicians, distinguished Muslim scholars and academics.
One of his grandfathers was a grand imam of Al Azhar, the highest seat of learning in Sunni Islam. His maternal grandfather was a president of Cairo University.
One of his two brothers, Mohammad, is a dermatologist, and his twin sister Heba is an oncologist.
Al Zawahiri studied ophthalmology at Cairo University and worked as an eye surgeon for several years in his clinic in Cairo’s Maadi suburb.
In his teenage years, he joined the Muslim Brotherhood and was much influenced by Sayyid Qutob, the lead ideologue of the group, whose extremist theories inspired generations of terrorist and Islamist leaders.
Qutob was hanged in 1966 in connection with an attempt on the life of Egyptian president Gamal Abdel Nasser.
A life of terror
Despite a reputation for an inflexible and combative personality, Al Zawahiri managed to nurture loosely affiliated groups around the world that grew to wage devastating insurgencies and attacks.
The terrorism destabilised a number of countries across Asia, Africa and the Middle East.
The first time the world heard of Al Zawahiri was when he stood in a courtroom cage after the assassination of Egyptian president Anwar Al Sadat in 1981.
Al Zawahiri served a three-year jail term for illegal arms possession, but was acquitted of the main charges.
He went to Pakistan on his release, where he worked with the Red Crescent treating mujahideen wounded in Afghanistan fighting Soviet forces.
During that period, he became acquainted with bin Laden, a wealthy Saudi who had joined the Afghan resistance.
Taking over the leadership of a militant group called Islamic Jihad in Egypt in 1993, Al Zawahiri was a leading figure in a campaign in the mid-1990s to overthrow the Egyptian government and set up a purist Islamic state. More than 1,200 Egyptians, mostly police officers, were killed.
Egyptian authorities took action against Islamic Jihad after an attempt on president Hosni Mubarak's life in June 1995 in Ethiopia.
Al Zawahiri soon responded by ordering attack on the Egyptian embassy in Islamabad, Pakistan. Two cars filled with explosives crashed through the compound's gates, killing 16 people.
In 1999, an Egyptian military court sentenced Al Zawahiri to death in his absence.