Six medium-range ballistic missiles were fired from western Iran at 2 am (10.30am GMT Sunday), dealing a "fatal blow 570 kilometres away" said the Guards.
Iranian state television and the state-run IRNA news agency said the missiles "killed and wounded" militants in Syria, without elaborating.
"This is the roaring of missiles belonging to the Revolutionary Guard of the Islamic Revolution", the state TV's reporter said as the missiles launched behind him.
In Monday's statement, the Guard said that based on evidence from the Ahvaz attack, the "terrorists" in eastern Syria are supported and guided by the United States in line with "satanic" plans of the White House, the Zionist regime - Iranian parlance for Israel - and a regional power, a reference to Saudi Arabia.
The attack was simultaneously claimed by the Saudi Arabia-linked al-Ahwaziya terrorist group, and the Daesh (ISIL or ISIS) Takfiri terror outfit, which is suspected of receiving Saudi patronage.
The strikes against the Islamic State on Monday, however, came even as Iran had blamed local Arab separatists for last month's attack in the southwestern city of Ahvaz.
Saudi Arabia and the UAE have denied involvement in the attack. The Revolutionary Guard said the missiles travelled some 350 miles from Iran's Kermanshah province to their targets in Syria.
"Terrorists used bullets in Ahvaz", Gen. Amir Ali Hajizadeh, chief of the Guard's aerospace division, told the semi-official Tasnim news agency.
Gareth Bale to miss Real Madrid's Champions League clash with CSKA Moscow
Bale did not come out for the second half at the Bernabéu after looking one of Real's more lively players during the first half. "You take into account the statistics and make a decision".
Boukamal is held by Syrian government forces, but IS still maintains a presence in the area, despite being driven from virtually all the territory it once held in Syria and Iraq. It added that seven drones were also used to bomb rebel targets during the attack, which killed a number of fighters and destroyed supplies and infrastructure used by the group.
The U.S. military's Central Command confirmed that Iranian forces conducted "no-notice strikes last night".
Strong explosions shook the area in the early hours of Monday, reverberating east of the Euphrates River, he said.
"At this time, the coalition is still assessing if any damage occurred and no coalition forces were in danger", spokesman Sean Ryan said.
Iranian President Hassan Rouhani had promised a "crushing" response to the September 22 attack by five gunmen on the military parade in Ahvaz, a mainly ethnic Arab city, while the Guards threatened "unforgettable revenge".
But both the Islamic State and a local separatist group claimed responsibility for the attack.
Last year, the IRGC said it targeted IS members in Syria with missiles after the extremist group took responsibility for twin attacks on Iran's parliament and the mausoleum of Islamic republic founder Ruhollah Khomeini that left 18 people dead. The United Nations says Iran still honors the terms of the accord, in which it limited its enrichment of uranium in exchange for the lifting of economic sanctions.
At least one of the missiles #Iran launched from outside the Kurdish city of Kermanshan exploded moments after it was sacked and landed in the outskirts of the city.