The attacks have been carried out in the central province of Homs and comes as president Bashar al-Assad’s forces reclaimed the historic Palmyra castle.
Russian Aerospace said there were 40 sorties near the ancient city over the last 24 hours.
In a statement it said: “Strikes were carried out on 158 terrorist targets, resulting in 100 militants killed.
“Four tanks, three artillery mounts, four ammo storage depots and five motor vehicles were destroyed.”
Syrian forces, supported by Vladimir Putin’s forces, have gained much ground against the ISIS insurgents, recapturing the town of Al-Amiriyah after fierce clashes.
The successful operation came just days after the pro-ISIS group’s attacks on Brussels, which left 31 dead in the Belgian capital.
Palmyra fell to ISIS, also known as Daesh, last summer.
The allied forces and the Syrian government have been attempting to reclaim it for the last month.
Irina Bokova, of UNESCO, said: “I welcome the liberation of the Palmyra archeological site, martyr city inscribed on the UNESCO World Heritage List, which carries the memory of the Syrian people, and the values of cultural diversity, tolerance and openness that have made this region a cradle of civilization.”
After ISIS took hold of Palmyra it destroyed ancient buildings and carried out brutal executions at historical sites.