WASHINGTON - In what could be one of the hardest blows to al Qaeda since the U.S. campaign against the terrorist organization began, the group's No. 3, Sheikh Sa'id al-Masri, is believed to be dead, killed by a U.S. Predator drone strike, a U.S. official said yesterday.

The official, speaking on condition of anonymity, said word was "spreading in extremist circles" of his death in Pakistan's tribal areas in the past two weeks.

There were multiple postings on Jihadist websites by al-Qaida's so-called General Command, announcing his death, according to both the IntelCenter and SITE Intelligence Group. SITE said yesterday's announcement also stated that his wife, three of his daughters, his granddaughter, and other men women and children were killed.

Al-Masri 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-Masri, also known as Mustafa al-Yazid, was the group's prime conduit to Osama bin Laden and Ayman al-Zawahiri, and he was key to day-to-day control, with a hand in everything from finances to operational planning, the U.S. official said.

The official says his death would be a major blow to al Qaeda, which in December "lost both its internal and external operations chiefs."

Al-Masri has been one of many targets in a U.S. Predator-drone campaign aimed at militants in Pakistan since President Obama took office. The Egyptian-born militant made no secret of his contempt for the United States, once calling it "the evil empire leading crusades against the Muslims."

The shadowy, 55-year-old al-Masri has been involved with Islamic extremist movements for nearly 30 years since he joined radical student groups led by fellow Egyptian al-Zawahiri, 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-Masri turned up in Afghanistan, where, according to al Qaeda's propaganda wing Al-Sabah, he became a founding member of the terrorist group.

He later followed bin Laden to Sudan and back to Afghanistan, where he served as al-Qaida's chief financial officer, managing secret bank accounts in the Persian Gulf that were used to help finance the Sept. 11, 2001, attacks on New York and Washington.