Al-Qaeda's second-in-command has purportedly called for attacks against Pakistan in revenge for the army's assault on Islamabad's Red Mosque.
Zawahiri is thought to be in hiding on the Afghan-Pakistan border
In a video recording released on an Islamist website, a voice said to be that of Ayman al-Zawahiri calls the siege of the mosque a crime.
"Your salvation is only through jihad [holy war]," the speaker on the tape says, over an image of Zawahiri.
At least 83 people died when troops cleared the mosque of militants.
"This crime can only be washed away by repentance or blood," says the voice on the tape.
"If you do not revolt, [Pakistan's President Pervez] Musharraf will annihilate you," the recording warns.
"Musharraf will not stop until he uproots Islam from Pakistan."
Pakistani officials said on Wednesday that the bodies of 73 people, including one its most militant clerics, Abdul Rashid Ghazi, were found at the Red Mosque, or Lal Masjid.
Ten soldiers were also killed as they stormed the mosque complex.
Zawahiri and al-Qaeda chief Osama Bin Laden are believed to be hiding in the rugged mountainous tribal area along the border between Pakistan and Afghanistan.