It was the first missile attack by Iran outside its own territory in 30 years, since the Iran-Iraq war of 1980-88, media in the Islamic republic reported.
"Medium-range missiles were fired from the (western) provinces of Kermanshah and Kurdestan, and a large number of terrorists were killed and weapons destroyed", the statement said.
The Revolutionary Guards are fighting in Syria against militant groups who oppose President Bashar al-Assad.
The Guard warned ISIL militants and their "regional and global supporters" that similar retaliatory attacks would target them as well if another assault in Iran occurred.
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"The spilling of any innocent blood will not go unanswered", Press TV cited a statement by the Revolutionary Guards as saying.
Activists in Syria did not immediately have information about the Iranian-claimed strikes.
The Daesh Takfiri terrorist group claimed responsibility for the assaults.
The Islamic State launched two coordinated attacks against Iran's Parliament and tomb of Ayatollah Khomeini on June 7 in Tehran.
Iran has described the attackers as being "long affiliated with the Wahhabi", an ultraconservative form of Sunni Islam practiced in Saudi Arabia.