Who could succeed al-Qaeda's Ayman al-Zawahiri?

The United States killed al-Qaeda leader Ayman al-Zawahiri with a drone missile while he stood on a balcony at his home in downtown Kabul, Afghanistan, officials in Washington said, the biggest blow to the militants since Osama bin Laden was shot dead in 2011.

Here are some top contenders to take over the militant organisation, according to experts.

Saif al-Adel

The mysterious, low-key former Egyptian special forces officer is a high-ranking member of al-Qaeda.

The United States is offering a reward of up to $10 million for information leading to his arrest.

Al-Adel was suspected of involvement in the assassination of Egyptian President Anwar Sadat in 1981, and left the country in 1988 to join the mujahideen fighting Soviet occupation in Afghanistan.

Read | Ayman al-Zawahiri: From a trained surgeon to Al-Qaeda leader

One of al-Qaeda's leading military chiefs, and often called the third-ranking al-Qaeda official, al-Adel helped to plan the bomb attacks against the American embassies in Nairobi and Dar as Salaam in 1998 and set up training camps for the organisation in Sudan, Pakistan and Afghanistan in the 1990s.

In 2004, al-Adel's diary was recovered during a raid in Saudi Arabia. His role in the organisation has been as a trainer, military leader and member of bin Laden's security detail.

Before joining al-Qaeda he was a member of Egypt's Islamic Jihad organisation, which was bent on toppling the state.

Al-Adel was linked to the killing of U.S. journalist Daniel Pearl in Pakistan in 2002, U.S. investigators said in a report.

The findings by investigators of the Pearl Project revealed al-Adel had discussed Pearl's abduction with Khalid Sheikh Mohammad, also known as KSM, the accused mastermind behind the September 11, 2001, attacks on the United States.

Al-Adel was appointed caretaker leader after the death of bin Laden.

Yezid Mebarek

Yezid Mebarek, known as Abu Ubaydah Yusuf al-Anabi, succeeded as emir of al-Qaeda in the Islamic Maghreb in 2020, when a French raid killed his predecessor, after running one of the group's leadership councils and sitting on another.

An Algerian citizen, Mebarek ran media operations for AQIM, using a 2013 video to call for global attacks against French interests after Paris sent troops to help quash a militant insurgency in Mali.

Mebarek, 53, pictured in one photograph with a full grey beard and green turban, is a veteran of Algeria's 1990s civil war between the government and Islamist forces, rising through the ranks of a militant splinter group, the GSPC.

AQIM took advantage of chaos across the Sahel region to become one of the global network's most active and valued branches, kidnapping Westerners and staging attacks across swathes of territory.

As a mark of AQIM's importance to al-Qaeda, Mebarek's predecessor as its chief Abdelmalek Droukdel, served a role in the global movement's leadership team under Zawahiri, before being killed by French forces in 2020.

However, analysts believe AQIM has lost sway to newer militant groups in the Sahel, one of the world's most important arenas of jihadist activity, while Mebarek is reported to suffer from old injuries and to lack the charismatic pull of Droukdel.

Abd al Rahman al-Maghrebi

Moroccan-born national Abd al-Rahman al-Maghrebi is wanted for questioning by the FBI in connection with his membership in Al-Qaeda. He studied software programming in Germany before moving to Afghanistan where he was selected to manage al-Qaeda's main media wing, said the FBI. The son-in-law of Zawahiri, he is a senior al-Qaeda leader.

Documents recovered in the operation that killed Bin Laden indicated al-Maghrebi had been a rising star in the group for many years. He served as al-Qaeda's general manager in Afghanistan and Pakistan.