A media outlet affiliated with the terror group claimed on May 15 that ISIS hit the strategic T4 base in central Syria between the cities of Homs and Palmyra.
The global intelligence firm Stratfor
also released a series of images that purport to show damaged aircraft and supply depots at the base, which the group calls one of the "most important" in the country.
"The attack, and the considerable losses on the Russian side, stress the continued threat to supply lines for Russia and regime forces," Stratfor said.
Stratfor says the images show the damage incurred was likely not accidental.
"A range of separate locations within the airfield were targeted very accurately, with no sign of damage in the areas separating them," it said. "A single accidental explosion would not have been able to have this result."
In a statement emailed to CNN, Russia's Defense ministry denied that its forces came under attack, saying the satellite images show damage that "resulted from the battle for this airbase between Syrian government troops and rebels" and had "been there for a while."
"All Russian military helicopters that are currently in Syria are on the planned mission to destroy terrorists," the statement said. "[There have been] no losses among personnel at the Russian airbase."
Pentagon spokesman Col. Steve Warren told CNN it's unclear what happened.
"ISIS has claimed responsibility but we're not clear if it was them or if it was an accident," he said.
A U.S. defense official told CNN that it appeared to be an accident that caused a chain reaction of explosions and not the result of enemy action.
Russia conducted its first airstrikes in Syria in September 2015. Its involvement helped solidify President Bashar al-Assad's military advantage.
Russian officials say they are fighting terrorists, but the U.S. and others have accused them of also targeting moderate Syrian elements that are fighting the government.
Didn't Russia leave Syria?
Russia announced it would withdraw its forces in Syria in March
, and planes began leaving the next day.
However, Russia still has a sizable presence in Syria.
CNN's Frederik Pleitgen was one of more than a hundred foreign journalists earlier this month invited to Palmyra, a city which Russia seized in March after ISIS captured it last year.
"While the exact size of Russia's military presence in Syria is still unclear, the things we saw while embedded with them indicate that it is bigger and more sophisticated than most believe," Pleitgen said
. "It does not look like an army that plans on leaving Syria any time soon."
So why announce a withdrawal only to stay?
Syria is still an important geostrategic asset for Russia, according to Leon Aron, the director of Russian studies at the American Enterprise Institute.
And maintaining a military presence in Syria could help Russia position itself as a dominant player in the Middle East.
The war has also been incredibly popular in Russia, boosting Putin's popularity.
"The Russian President has tapped into the imperial nostalgia of millions of Russians and, with the help of monopolistic propaganda, he has become the symbol and embodiment of 'Russia rising from its knees' to recover the Soviet Union's position of superpower," Aron says.
"Putin has saddled the tiger of patriotic mobilization and has expertly made it trot in the right direction ... Short of the tiger turning herbivore, Putin is not leaving Syria.