Ayman al-Zawahiri and al Qaeda have been blamed for numerous terrorist attacks worldwide, mainly on Western targets, including the attacks of September 11, 2001, on New York and Washington that killed nearly 3,000 people. Read the full profile
Here's a timeline of some of the charges against al-Zawahiri and key points in his life:
* 1970s – al-Zawahiri works to overthrow Egyptian President Anwar Sadat, and establish an Islamic state.
* 1979 – Travels to Afghanistan to offer his services as a doctor to the rebels fighting the Soviet Union.
* 1981 – After Sadat's assassination, al-Zawahiri is imprisoned on conspiracy charges. He is eventually acquitted.
* 1987 – Al-Zawahiri and Osama bin Laden meet for the first time, in Pakistan. FULL POST
Ayman al-Zawahiri has been appointed the new leader of al Qaeda, according to a statement posted on several jihadist websites.
Al-Zawahiri has played a defining role in al Qaeda for more than a decade as Osama bin Laden's deputy. Even before the announcement, he had been widely regarded as the organization's de facto leader.
The announcement, dated June 2011 but which surfaced Thursday on the sites, said the decision to appoint al-Zawahiri was made to pay respect to the "righteous martyrs" and to honor the legacy of bin Laden.