Maamoun Abdulkarim, the head of the government's Antiquities and Museums Department, told The Associated Press that the extremists destroyed the grave of Mohammad Bin Ali, a descendant of Imam Ali, cousin of Islam's Prophet Muhammad and a deeply revered Shiite saint.
The grave was just north of Palmyra.
The second tomb is close to the city's famed Roman-era archaeological site and was the final resting place of a Sufi scholar, Nizar Abu Bahaa Eddine, who lived in Palmyra some 500 years ago.
