US operation kills al Qaeda's top leader, who has led the terror group since bin Laden was killed in 2011

• The leader of al-Qaida, Ayman al-Zawahiri, was killed in a US drone strike in Afghanistan.
• The strike took place over the weekend in Kabul, Politico and the AP reported.

The leader of al-Qaida has been killed by a US drone strike in the Afghan capital of Kabul, according to news reports Monday.

In a statement reported by Politico, a Biden administration official said that over the weekend "the United States conducted a counterterrorism operation against a significant [al-Qaida] target in Afghanistan."

A source familiar with the matter told the Associated Press that the target was Ayman al-Zawahiri. The FBI listed Zawahiri, 71, as a "most wanted terrorist" with a reward of up to $25 million for information leading to his apprehension or conviction.

Zawahiri, who was born in Egypt, was Osama bin Laden's no. 2. He became Al Qaeda's leader after Navy SEALs killed bin Laden in a raid back in 2011. National security experts said Zawarhiri lacked the charisma of bin Laden, and wasn't as effective as a leader.

According to the FBI, Zawahiri was a doctor and founder of the militant group the Egyptian Islamic Jihad, which merged with al-Qaeda in 1998. He was indicted for the Aug. 7, 1998, bombings of the U.S. embassies in Kenya and Tanzania.

After the attacks of 9/11, as bin Laden took on a less visible role with al-Qaeda, Zawahiri emerged as the behind-the-scenes operative of the terror group, according to The Washington Post.

"Zawahiri is used to dominating from behind the scenes," Jarret Brachman, research director of the Combating Terrorism Center at the U.S. Military Academy at West Point told The Washington Post in 2006. "In my opinion, he's sort of like the Dick Cheney of al-Qaeda."

The news of Zawahiri's death comes nearly one year after the US withdrew its troops from Afghanistan following two decades of war, an event that coincided with the Taliban regaining control of the country.

Biden at the time declared that the war in Afghanistan was over, though he also said the US would maintain the fight against terror groups in the country — just without boots on the ground. The president signaled that the US would continue to target terrorists with drones and airstrikes, as part of an "over-the-horizon" strategy. Critics said this was a sign that the war wasn't really over, despite Biden's claims to the contrary.

"The likelihood is that the Taliban will provide a safe haven for terrorists in Afghanistan, which means that this war is not over," Leon Panetta, who served as both CIA director and defense secretary during the Obama administration, said in an interview with MSNBC's Andrea Mitchell last year.

Though the Biden administration says there were no civilian casualties in the operation that killed Zawahiri, human rights groups have expressed concerns that Biden's "over-the-horizon" strategy for continuing to go after terror groups without boots on the ground could lead to more civilian deaths.

"I'm definitely concerned that the Biden administration's 'over-the-horizon' approach will result in more civilian casualties because the accuracy of drone strikes depends heavily on the quality of intelligence, and if the US does not have an actual presence in Afghanistan, it's hard to see how it can determine whether the information it's getting from any supposed partners on the ground is reliable," Daphne Eviatar, Amnesty International USA's director of Security With Human Rights, told Insider last September.