A U.S. official says al-Qaida's number two leader, Atiyah Abd al-Rahman, has been killed in Pakistan.

The official, who spoke on the condition of anonymity, said Saturday Rahman was killed on August 22 in Pakistan's northwestern tribal region of Waziristan — a known refuge for Taliban and al-Qaida-linked militants.

The official would not say how Rahman was killed.

Pakistani security officials said on August 22 that a U.S. drone strike that day killed four suspected militants near the town of Mir Ali in North Waziristan.

Rahman rose to al-Qaida's number two spot after U.S. special operations forces killed the network's leader, Osama bin Laden, during a raid on his Pakistan compound in May. In June, al-Qaida picked Ayman al-Zawahri to succeed bin Laden as head of the terror organization.

The U.S. official said Saturday Zawahri was relying on Rahman to help run al-Qaida.

Last month, U.S. Defense Secretary Leon Panetta said the defeat of al-Qaida is within reach if the U.S. military could mount a series of successful attacks on the group's leadership.