The cause of the fires is unconfirmed.
A Russian opposition website quoted Syrian sources as saying "a large fire in the Syrian part of the T4 airbase spread to the fleet of vehicles, and after a fuel tank exploded four Russian helicopters nearby went up in flames".
"The cause of the fire is being established," it added.Regardless of what triggered the fire that destroyed four Russian attack helicopters at their central Syrian base, this is the most serious loss for the Russians so far in their engagement against IS.
Speculation that the fire was accidental was fueled by the first report of the incident, which came from Amaq, a news agency linked to IS, says BBC Arabic's Syria correspondent Rami Ruhayem.
"Burning of four Russian attack helicopters and 20 trucks loaded with missiles inside T4 airport in eastern Homs [province] as a result of a nearby fire," the report said, without identifying the cause.
On the same day, IS released an image it said showed one of its fighters firing Grad rockets at T4, also known as Tiyas.
"What the imagery tells us is that first of all this was not an accidental explosion, as some of the rumours kept saying," Stratfor military analyst Sim Tak said.
"It shows very clearly that there are several different sources of explosions across the airport, and it shows that the Russians took a quite a bad hit.
"An entire combat helicopter unit was wiped out - four helicopters in total - as well as some damage to some of the Syrian planes on the airport, and also very notably a logistic depot, likely one that was being used to supply those specific combat helicopters."
Tak described Amaq's account as "very accurate", and suggested the helicopters and depot were destroyed by IS attacks.
He said it was unclear why IS had not officially said it had caused the destruction.Tak said it "would really be a marginal, almost non-existent chance for this to be accidental".
Russia has not officially commented on the incident.