The monitors said IS was taking advantage of the annual harvest of the desert fungus delicacy, which typically runs from February to April, to carry out attacks in remote locations.
The IS group did not immediately claim the attack through its normal channels.
Syrian state media on Friday reported 53 dead after the attack on the southwestern city of al-Sokhna.
It was IS’s deadliest attack since January last year, when it stormed a prison in the Kurdish-controlled northeastern city of Hasakeh to free fellow jihadists.
Fighting inside the city killed 105 people, mostly civilians, as well as 268 jihadists.