Pakistan has condemned a taped message attributed to Osama Bin Laden's deputy which urged Muslims in Pakistan to overthrow President Pervez Musharraf.
Many tapes have been attributed to Bin Laden and Zawahri
A spokesman in Islamabad said such threats would not deter Pakistan from its campaign against al-Qaeda.
In the message, broadcast by two Arabic TV stations on Sunday, a voice said to belong to Ayman al-Zawahri accuses General Musharraf of betraying Islam.
It was the second such tape attributed to al-Qaeda's deputy aired this month.
"Al-Qaeda is a terrorist organisation," said Pakistani
Foreign Ministry spokesman Masood Khan.
"Pakistan is part of the war on terrorism, and our pursuit of terrorists,
al-Qaeda and their associates, will continue despite these
Some opposition groups have also condemned the message, saying al-Qaeda had no right to interfere in Pakistan's internal affairs.
The previous tape, which CIA experts later assessed as authentic, was broadcast on 10 September as Americans prepared to mark the second anniversary of the attacks on New York and Washington.
Ayman al-Zawahri was also featured with the al-Qaeda leader in video footage that emerged at the same time in which the two men urged fighters to turn Iraq into a graveyard for US troops.
Reports suggest the latest tape was recorded recently as it refers to a visit to India by Israeli Prime Minister Ariel Sharon and the resignation of Mahmoud Abbas as Palestinian prime minister earlier this month.
"Muslims in Pakistan must unite and co-operate to topple this traitor and install a sincere leadership that would defend Islam and Muslims," the speaker on the tape said.
He also accused General Musharraf of making it possible for the US to "kill thousands of innocents in Afghanistan."
Pakistani security forces have co-operated closely with the US in efforts to track down Osama Bin Laden and other al-Qaeda supporters in areas on the Afghan border where they could be hiding.
Another part of the tape makes lengthy reference to a US Congress report on the 11 September attacks which was not published in full.
According to al-Jazeera, Ayman al-Zawahri says the omitted portion asked for Saudi Arabia to stop printing copies of the Koran because it was full of provocations.
Leaks to the US media at the time of the report's publication in July this year strongly suggested that the missing pages related to allegations about Saudi support and involvement in the 11 September plot.