Report: Al-Qaida No. 2 may be dead

ISLAMABAD, Pakistan, Aug. 2 (UPI) -- Ayman al-Zawahiri, believed to be al-Qaida's second-in-command, may be critically injured or killed in Pakistan, CBS News reported Saturday.

The network says it has obtained a copy of an intercepted letter sent by a Taliban commander in Pakistan's South Waziristan province saying that Zawahiri was in "severe pain" and that his "injuries are infected." The Taliban letter was dated July 29, the day a U.S. air strike in Pakistan's remote frontier region killed al-Qaida weapons expert Abu Khabab Masri.

CBS says the letter was reportedly written by Pakistani Taliban leader Baitullah Mehsud. The network adds that unidentified sources have told it U.S. counter-terrorism experts are investigating the possibility Zawahiri has been killed.

Zawahiri, a surgeon who reportedly led a merger between the Egyptian Islamic Jihad group and Osama bin Laden's al-Qaida terrorist organization in 1998, is thought to be bin Laden's chief lieutenant. Zawahiri was also thought to have been killed in a 2006 U.S. airstrike but later resurfaced in a video, officials said.