ATTACK MAY HAVE KILLED AL-ZAWAHIRI

Breaking news:

An online report says U.S. government sources are trying to confirm that an airstrike in northwestern Pakistan has killed al-Qaida's deputy leader, Ayman Zawahiri.

According to the subscription report at Stratfor, the airstrike was on July 28, and sources were reporting that an announcement from the U.S. government is expected soon.

The report said the attack was carried out by a U.S. Predator attack plane.

According to the blog Jawa Report, officials had said earlier "the hunt was on" in Pakistan for a "big fish."

UPDATE: From Fox News:

Al Qaeda’s second in command, Ayman al-Zawahiri, may be injured or even dead, according to a CBS News report based on an intercepted letter that urgently requests a doctor to treat Zawahiri.

CBS News says it obtained a copy of the letter from sources in Pakistan, where Zawahiri, second only to Usama bin Laden, is thought to be hiding.

The letter, reportedly written by a local Taliban leader and dated Tuesday, says Zawahiri is in "severe pain" and his "injuries are infected," according to the report.

A missile strike Monday in Pakistan’s tribal areas reportedly killed Al Qaeda operative Abu Khabab al-Masri, considered a "Top Ten" target as the terrorist organization’s top expert on chemical and biological weapons.

That strike also killed five others, though it isn’t clear whether Zawahiri was at the scene or in the area.