The victims, who played for popular team Al-Shabab, were beheaded in front of a crowd of children in Raqqa after they were accused of spying for the Kurdish YPG.
Gruesome pictures of the execution - which shows children inspecting the bodies of the victims - were posted on a dissedent group`s Twitter feed.
In a series of tweets, Raqqa is Being Slaughtered Silently named the victims as Osama Abu Kuwait, Ihsan Al Shuwaikh, Nehad Al Hussen and Ahmed Ahawakh.
They shared pictures of the men in their Al-Shabab kits.
Another unnamed man was also executed.
ISIS banned organised sports including football when they took over Raqqa two years ago.
Last year ISIS militants executed 13 teenage boys for watching the Asian Cup football match between Iraq and Jordan last week.
The young football fans had been caught watching the game on television in the Iraqi city of Mosul, which is controlled by the Islamic State.
The teenagers were rounded up and publicly executed by a firing squad using machine guns, anti-ISIS activist group Raqqa is Being Slaughtered Silently reported.
ISIS behead four footballers in Syria after accusing them of spying for Kurdish rebels
09 July 2016
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ISIS militants have executed four footballers in Syria after its religious leaders said supporting football was anti-Islamic.
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