Stratfor said its satellite images appeared to confirm that Russian military choppers and other vehicles had been destroyed.

The Texas-based, American publisher and global intelligence company, Stratfor said on its website: "it is clear from the imagery that the northeastern part of the T4 air base, the section of the airport where helicopter use is concentrated, sustained considerable damage."

In a report published on Tuesday, the intelligence firm said in addition to the Russian technology, a Syrian MiG-25 aircraft that was likely already out of commission appeared to have been damaged.

Stratfor said the destruction of the helicopters at the base was “a stark reminder of the constant threat” that Russia, a key ally of Syrian President Bashar al-Assad, faced in its mission in Syria.

The so-called "Islamic State" (IS) group claimed their fighters had attacked the base on May 14. The jihadist group said four Russian attack helicopters and 20 trucks loaded with ammunition were destroyed at the T4 base, in Homs province.

Russia has not officially commented on this incident, leading to questions about what exactly happened.

Not an accident

The BBC later quoted Stratfor analyst Sim Tack as saying that "this was not an accidental explosion". It "would really be a marginal, almost non-existent chance for this to be accidental," he added.

The Syrian Observatory for Human Rights had reported shelling of the T-4 base on May 11 after IS jihadists briefly took control of part of a route between Palmyra and Homs.

The British-based observatory also said two days later that continued shelling had caused an explosion at a fuel depot and a fire destroyed three helicopters.

The first report of the base attack came on May 15, when the IS-affiliated Amaq news agency claimed an assault had taken place.