In a video found on Islamist websites late Wednesday, Al-Zawahiri called on all Afghans, particularly students in universities and schools in Kabul, to stand up for Islam and Afghanistan.

Hours later, Afghanistan's President Hamid Karzai described al-Zawahiri an enemy of the Afghan people and blamed him for his country's massive suffering.

''I am calling upon the Muslims in Kabul in particular and in all Afghanistan in general and for the sake of God to stand up in an honest stand in the face of the infidel forces that are invading Muslim lands,'' Osama bin Laden's deputy said in the three-and-a-half minute video, which shows him seated wearing a white turban, with a automatic rifle next to him.

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He also called on ''the young men of Islam, in the universities and schools of Kabul, to carry out their duties in defence of their religion, honour, land and country.''

''I direct my speech today to my Muslim brothers in Kabul who lived the bitter events yesterday and saw by their own eyes a new proof of the criminal acts of the American forces against the Afghani people,'' al-Zawahiri said on the recording, titled 'American Crimes in Kabul.'

He appears to be referring to the US military vehicle which crashed into traffic in Kabul May 29, killing at least seven people. At least 20 people were killed in the anti-foreigner riots that followed, the highest toll in the capital since the Taliban was routed from the country in 2001.

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Unlike al-Zawahiri's previous messages, (this is his sixth this year) this one has no English subtitles. His spoke in Arabic, and the terrorist Web sites ran translations in Pashtun and Farsi, languages widely spoken in Afghanistan.

On Thursday, the US military said four US soldiers have been killed and one wounded in clashes with Taliban insurgents in eastern Afghanistan.

Last week, coalition and Afghan forces launched Operation Mountain Thrust, a huge offensive which involves more than 10,000 Afghan, British, Canadian and American troops, as well as Afghan soldiers, to flush out extremists from southern Afghanistan.

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