A letter, posted an a Web site used by Islamic militants, allegedly by Omaima Hassan praised Muslim women for their role in the political upheavals that gripped much of the Middle East last year.
"I congratulate all females of the world for these blessed revolutions and I salute every mother who sacrificed her loved ones in the revolutions," the message was quoted by al-Arabiya as stating. "It is really an Arab Spring and will soon become an Islamic Spring."
Zawahiri took control of al-Qaida after Osama bin Laden was killed by U.S. forces in Pakistan last year.
The White House confirmed Tuesday that Abu Yahya al-Libi, al-Qaida's No. 2 man, was killed in Pakistan.
An unidentified U.S. official told The Washington Post al-Libi was killed in a drone strike but White House press secretary Jay Carney refused to confirm the manner of the militant leader's death.
Al-Qaida militants have been tied to some of the political violence gripping Syria and Yemen.