The elderly Sheikh Mohammad Said Ramadan al-Buti, reportedly in his 90s, was killed in an attack on the Ummayyad Mosque in the capital, reported Reuters, as was his grandson.
Syrian TV raised the death toll for the attack to 42, while 84 people were reported injured, said Reuters.
The Los Angeles Times said he had been speaking at the mosque at the time of the attack.
The violence comes as Assad battles an armed rebellion against his rule. An estimated 70,000 people have been killed in Syria over the past two years, bloodshed that continues despite international outcry.
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Efforts by the United Nations and others to help end the violence there have not been successful.
Watch a video of the aftermath at the mosque below, courtesy of The Guardian and Globalpost
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