Yazid, al-Qaida's leader in Afghanistan for the past three years, was a founder member of the terror network back in the late 1980s and a close confidante of Osama bin Laden.
"Al-Masri was the group's chief operating officer, with a hand in everything from finances to operational planning," a US official said. "He was also the organisation's prime conduit to bin Laden and (al-Qaida number two Ayman) Zawahiri," he said. "He was key to al-Qaida's command and control."
Yazid, 54, also known as Sheikh Said al-Masri, was on the list of individuals and organisations whose assets were frozen in the wake of the Sept 11, 2001 attacks on the United States. According to the FBI, it was Yazid who transferred funds via Dubai for Mohammed Atta, Marwan al-Shehhi and Wal al-Shehri, three of the hijackers who flew aircraft into the Twin Towers and the Pentagon.
But the September 11 commission quoted sources as saying that Yazid, described as al-Qaida's chief financial manager, had backed Taliban leader Mullah Omar in opposing the attacks "because he feared the US response."
The American official said that Yazid was "widely viewed" as al-Qaida's number three, although he does not figure on the FBI "10 most wanted terrorists" list or a State Department list of major terrorists with bounties on their heads.
Yazid, also a member of al-Qaida's Shura leadership council, appeared in a number of videos since he first emerged as the network's chief in Afghanistan in May 2007, wearing thick glasses and a white turban.