Russia has dismissed as “propaganda” claims that the Islamic State (ISIS/ISIL) destroyed four Russian helicopters and 20 supply trucks deployed to a military airbase in Syria which is loyal to dictator Bashar al-Assad.

Meanwhile, Fox News reports that unnamed U.S. officials suggested an “accidental fuel tank explosion” destroyed the Russian military equipment, not ISIS.

Russian helicopters in Syria “are performing their planned missions to destroy terrorists,” said Maj. Gen. Igor Konashenkov, a spokesman for the Kremlin’s defense ministry, the Associated Press (AP) reports.

Maj. Konashenkov said allegations by ISIS that it bombed Russian helicopters and trucks at the T4 airbase, also known as Tiyas, amounted to “propaganda.”

The Russian spokesman indicated that the “satellite images showing burned shells of helicopters and trucks at the [Tiyas] airbase reflect the damage from months of clashes in the area between Syrian government forces and militants,” according to AP.

On Tuesday, private intelligence firm Stratfor reported that satellite images it obtained “verifies that the T4 air base was severely damaged by an Islamic State artillery attack,” adding that “four Russian Mi-24 attack helicopters appear to have been destroyed.”

However, one U.S. official told Fox News, “The Stratfor analysis is wrong,” and another official added, “There is no indication that an ISIS attack took place.”

Early this month, the jihadist group claimed to have destroyed Russian equipment during an attack on the T4 facility located near the ancient city of Palmyra, which was recently retaken from ISIS by Russian-backed Assad forces.

“In early May, the Islamic State launched an operation to capture the Shaer natural gas field northeast of the air base,” reported Stratfor. “After doing so, the group advanced south, seeking to cut off loyalist forces in Palmyra by severing a road that leads west from Palmyra, passes by the T4 air base, and continues toward Homs city.”

ISIS bombed the T4 base in Homs province repeatedly despite failing to cut off the Syrian troops for long, added the intelligence firm.

Stratfor noted that it had acquired the satellite pictures in collaboration with AllSource Analysis.

“Russian forces have deployed a contingent of attack helicopters to the T4 air base at least since March 2016, supporting the loyalist offensive to retake Palmyra that same month,” it said. “Based on satellite imagery as well as video of the base, the Russian force consisted of approximately four Mi-24P gunships. So at least according to these open sources, no Syrian Mi-24 helicopters operated from the T4 air base in recent months.”