The video by Ayman al-Zawahri - which would be his sixth this year - was posted Wednesday evening on an Islamic Web site known as a clearing house for al-Qaida and other militants' statements.
In the video, al-Zawahri is wearing a white turban and sitting in front of a black backdrop with an automatic rifle next to him, according to IntelCenter. The firm did not say how it obtained the video.
The 3 1/2-minute tape appears to have been made the day after a May 29 accident in which a U.S. military truck crashed into traffic in Kabul, killing up to five people. The incident sparked anti-foreigner riots in Kabul that left about 20 people dead - the deadliest unrest in the Afghan capital since the fall of the Taliban in 2001, the AP reports.
"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-Zawahri said in the videotape.