Sources said more than 30 others were injured when several mortars fired by the extremists struck the al-Mashhad neighborhood of the city on Wednesday.
The attack came as people gathered in the city located some 355 kilometers (220 miles) north of Damascus to say Eid al-Fitr prayers marking the end of the holy Muslim fasting month of Ramadan.
President Bashar al-Assad joined Eid al-Fitr prayers at a mosque in Syria's third city Homs outside the capital for the end-of-Ramadan holiday.
Large parts of Homs were once under the control of foreign-backed militants but since May 2014 they have been confined to a single neighborhood in the city's outskirts.
The al-Safa mosque, where Assad joined worshipers, is in Akrama which has been hit by repeated attacks by Daesh and al-Qaeda-linked Nusra Front terrorists.
Official television broadcast footage of the president in the congregation alongside Islamic Endowments Minister Mohammad Abdel-Sattar Sayyed and Syria's top Muslim cleric Ahmad Badredine Hassoun.
Assad has attended almost all Eid prayers since the war erupted in 2011, but this was possibly his first public appearance for the occasion outside Damascus; Press TV reported.
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