"The atheist criminals have long used the most despicable, cruel and brutal means against Muslims in Turkistan," said Abu Yayha al-Libi, who is sometimes identified as the commander in Afghanistan of the international terrorist network Al-Qaida.
"Thousands of Muslims were killed, and no one knows about them," he said in the 20-minute video, referring to Uighurs living in China.
Muslims with historical and linguistic ties to the Turkic peoples of Central Asia, Uighurs live in the western Chinese province of Xinjiang, which Islamists call East Turkistan.
According to the Washington-based terrorism monitoring group IntelCenter, the tape was made around late July or early August and released Tuesday by al-Sahab Media, Al-Qaida's media arm.
Nearly 200 people were killed and thousands injured or arrested in clashes between Uighurs and Han Chinese in Xinjiang in July.
In August, the Turkistan Islamic Party, a Uighur separatist group that claimed responsibility for a 2008 bombing in Shanghai, used similar language to call for attacks in response to the "massacre" of Uighurs in Xinjiang.
"There is no path to salvation or toward lifting oppression and injustice save by returning to religion," al-Libi said. Muslims "must sincerely prepare for jihad (holy war) and take up arms against the ruthless invaders".
"Consecutive Chinese governments have worked hard to sever every link between the wounded people of Turkistan and the Muslim nation," he said. "They are working to destroy them so that their numbers will decrease and their Islamic identity will be dissolved".
Al-Libi called for "a media campaign to tell the Muslim nation the truth about what is going on there and to expose Chinese colonialism".