Al-Qaida's deputy leader, Ayman al-Zawahiri, is second after Osama bin Laden on the F.B.I's list of most wanted terrorists.
The Egyptian-born doctor has become the terrorist organization's most senior spokesman -appearing in a series of video, audio and print messages over the past three months.
In his most recent comment broadcast on videotape last week by Arabic broadcaster al-Jazeera, Zawahiri called on President Bush to confess that the United States has been defeated in Iraq and Afghanistan.
Ayman al-Zawahiri was indicted for his alleged involvement in the 1998 bombings of U.S. embassies in Dar es Salaam, Tanzania and Nairobi, Kenya.
He founded the Egyptian Islamic Jihad, a group that opposes the secular Egyptian government and seeks to overthrow it through violent means.
Zawahiri has been on the run since late 2001 after U.S.-led forces invaded Afghanistan.Attack in Pakistan May Have Targeted Al-Qaida's No. 2 Man
Air strikes in Pakistan's remote tribal region may have killed several high-ranking al-Qaida figures, including the man considered the group's number two leader, Ayman Al Zawahiri. Unconfirmed reports from local and international news agencies are claiming Zawhiri, Osama bin Laden's top lieutenant, was the intended target of a missile attack that may have killed more than 18 people.
Several international and Pakistan news organizations say the attack early Friday targeted an al-Qaida safe house near Pakistan's border with Afghanistan.
The reports say that the United States ordered the strike after locating al-Qaida commander Ayman al-Zawahiri.
A U.S. Defense Department spokeswoman at the Pentagon says there are no reports of U.S. or allied military aircraft in the area of the attack.
U.S. diplomats in Islamabad would not comment on the matter.
Pakistan's Information Minister Sheikh Rashid Ahmed says his government is still gathering information.
"An investigation is on whether this high value target has been killed or not," he said.
Zawahiri has been on the run since late 2001, after U.S.-led forces invaded Afghanistan.
He and al-Qaida leader Osama bin Laden are thought to be hiding in the rugged mountains along the border.
U.S.-led forces in Afghanistan have come under frequent attacks from Taleban insurgents in the area.