US President Joe Biden has confirmed the death of Al Qaeda leader Ayman al-Zawahiri in a drone strike in Kabul, Afghanistan.
But who was the former leader of the terrorist group, and why is his death significant? Here are five quick questions to get you up to speed.
Who was Ayman al-Zawahiri?
An Egyptian doctor and surgeon, Ayman al-Zawahiri was the leader of the Al Qaeda terrorist group since 2011.
Along with Osama bin Laden, Zawahiri built the main infrastructure of Al Qaeda as a terrorist group, and he was considered crucial in the jihadi's movement, turning its focus to the United States, and plotting attacks against the country's civilians and military.
Zawahiri was largely considered to be the mastermind behind most of Al Qaeda's attacks, developing tactics and organisational skills needed to create militants around the world.
The 71-year-old was believed to have been the true architect behind the September 11 attacks in 2001, when four aircraft were hijacked and flown into the World Trade Center's twin towers, the Pentagon near Washington and a field in Pennsylvania, killing almost 3,000 people — the single deadliest terrorist attack in history.
Prior to September 11, Zawahiri was also believed to have plotted an attack on the USS Cole naval vessel in Yemen, which killed 17 US sailors and injured more than 30 others on October 12, 2000.
He had also previously been indicted for his role in bombing the US embassies in Kenya and Tanzania, which killed 224 people and wounded more than 5,000 others on August 7, 1998.
How important was he?
Zawahiri has been the leader of Al Qaeda since 2011, and took over after its founder, Osama bin Laden, was killed by US forces in Pakistan that year.
Prior to becoming leader, Zawahiri played a major role within the terrorist group, serving as its deputy leader since 1998.
After the US invaded Afghanistan in 2001, Zawahiri rebuilt Al Qaeda's leadership in the Afghan-Pakistan border region, and reshaped the group to become a decentralised operation, assembling networks of autonomous branches around the region.
Zawahiri was often seen as the face of the terrorist group, putting out constant streams of video messages while bin Laden was sheltered away.
Zawahiri also played a role in the 2004 train bombings in Madrid, and the 2005 transit bombings in London.
He was also considered by some to be a more prickly and divisive leader, with some key figures in Al Qaeda's leadership calling him overly controlling and secretive compared to bin Laden.
His death is widely considered to be the biggest blow dealt to the terrorist group since bin Laden's death 11 year ago.
Why was he wanted?
The FBI have had their sights on Zawahiri for decades because of his involvement in terrorist attacks targeting US nationals.
He had been on their Most Wanted Terrorists list for years for the murder of US nationals outside the United States, conspiracy to murder US national outside the United States, and attacking a federal facility resulting in death.
Before his death, the US Department of State offered a reward of $US25 million ($35.5 million) for information that led to his apprehension or conviction.
His whereabouts had been unknown until the strike, but he had been rumoured to be in either Pakistan's tribal area or inside Afghanistan.
There had been persistent rumours that he had died, but those were dispelled when a video released in April saw him praising an Indian Muslim woman for defying a ban on wearing an Islamic head scarf.
What do we know about the drone strike?
There is currently limited information about the strike, but sources have told Reuters that the CIA carried out a drone strike in the Afghan capital of Kabul on Sunday, local time.
"Over the weekend, the United States conducted a counterterrorism operation against a significant Al Qaeda target in Afghanistan," a senior administration official told Reuters.
"The operation was successful and there were no civilian casualties."
Speaking at the White House, US President Joe Biden confirmed the drone strike took place at 6:18am, local time, and said "justice has been delivered".
"People around the world people no longer need to fear the vicious and determined killer," Mr Biden said.
"We make it clear again tonight that, 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."
Mr Biden said the United States had located Zawahiri earlier this year, confirming he had moved to downtown Kabul to be with members of his immediate family.
On the ground, a loud explosion was heard in Kabul on Sunday morning.
"A house was hit by a rocket in Sherpoor. There were no casualties as the house was empty," Abdul Nafi Takor, spokesman of the interior ministry, said.
One Taliban source who spoke to Reuters said there had been reports of at least one drone flying over Kabul that morning.
A senior intelligence official told the Associated Press that Zawahiri was staying in a house owned by a senior Taliban leader, Sirajuddin Haqqani.
What has the reaction been to his death?
News of the strike was first confirmed by a spokesman from the Taliban, Zabihullah Mujahid.
He strongly condemned the drone strike, calling it a violation of "international principles" and the 2020 agreement on a US troop withdrawal.
"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 statement said.
Saudi Arabia has welcomed the death of the Al Qaeda leader, with a government spokesperson telling state media "Zawahiri is considered one of the leaders of terrorism that led the planning and execution of heinous terrorist operations in the United States and Saudi Arabia".
The US withdrew its troops from Afghanistan 11 months ago, two decades after it began its war in the middle eastern country.
ABC/wires
