A statement posted on the Web by Al-Qaeda said Al-Yazid, whom it described as the organization's top commander in Afghanistan, was killed along with his wife, three daughters, a grandchild and other men, women and children but did not say how or where.

The statement did not give an exact date for Al-Yazid's death, but it was dated by the Islamic calendar month of "Jamad Al-Akhar," which began in the second half of May.

A US official in Washington said word was "spreading in extremist circles" of his death in Pakistan's tribal areas in the past two weeks. His death would be a major blow to Al-Qaeda, which in December "lost both its internal and external operations chiefs," the official said on condition of anonymity because of the sensitivity of the information.

The Egyptian-born Al-Yazid, also known as Sheikh Saeed Al-Masri, was a founding member of Al-Qaeda and the group's prime conduit to Osama Bin Laden and Ayman Al-Zawahri. He was key to day-to-day control, with a hand in everything from finances to operational planning, the US official said.

Al-Yazid has been reported killed before, in 2008, but this is the first time his death has been acknowledged by the militant group on the Internet.

Al-Yazid has been one of many targets in a US Predator drone campaign aimed at militants in Pakistan since President Barack Obama took office. Al-Yazid made no secret of his contempt for the United States, once calling it "the evil empire leading crusades against the Muslims." "We have reached the point where we see no difference between the state and the American people," Al-Yazid told Pakistan's Geo TV in a June 2008 interview.

The shadowy, 55-year-old Al-Yazid has been involved with extremist movements for nearly 30 years since he joined radical student groups led by fellow Egyptian Al-Zawahri, now the No. 2 figure in Al-Qaeda after Bin Laden.

In the early 1980s, Al-Yazid served three years in an Egyptian prison for purported links to the group responsible for the 1981 assassination of Egyptian President Anwar Sadat. After his release, Al-Yazid turned up in Afghanistan, where, according to Al-Qaeda's propaganda wing Al-Sabah, he became a founding member of the terrorist group.