Ayman al-Zawahiri, the head of Al-Qaeda, was killed by an airstrike in Kabul, according to a statement issued by President Joe Biden on Monday, news agency AFP reported.
"Justice has been delivered and this terrorist leader is no more," Biden stated in a televised address.
Zawahiri, according to Biden, has "carved a trail of murder and brutality against American citizens."
According to officials, Zawahiri was on the balcony of a safe house when the drone launched two missiles at him, BBC reported.
Other family members were present, but they were uninjured, and they claimed that just Zawahiri was slain.
After months of planning, Biden announced he had granted final clearance for the "precise hit" on the 71-year-old al-Qaeda chief.
After Osama bin Laden's death in 2011, Zawahiri took headed al-Qaeda. He and Bin Laden collaborated in the 9/11 attacks, and he was one of the US's "most wanted terrorists."
According to Biden, his death will offer closure to the families of the 9/11 victims.
"No matter how long it takes, no matter where you hide, if you are a threat to our people, the United States will find you and take you out," Biden was quoted by BBC in its report.
Biden said Zawahiri was also responsible for other violent activities, such as the suicide bombing of the USS Cole naval warship in Aden in October 2000, which killed 17 US servicemen.
According to a Taliban spokesman, the US action is a flagrant breach of international law.
"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 spokesman was quoted by BBC in its report.
However, US authorities insisted that the operation was legitimate.
Ayman al-Zawahiri was an ideological brains behind al Qaeda's operations.
He was an Egyptian doctor who was imprisoned in the 1980s for his involvement in militant Islam. After his release, he fled the country and got active in violent international jihadist activities.
(With Inputs From Agencies)