Satellite imagery appears to show extensive damage to an air base in Syria used by Russian forces following an attack by fighters from the Islamic State group, US intelligence company Stratfor said Tuesday.
The claim was immediately denied by Russia's defence ministry which said that the damage had been there for months and was due to fighting between Syrian government forces and "militants from terror groups".
Stratfor released satellite images dated from May 14 and May 17, implying that the damage to the T-4 base, also known as Tiyas, was caused in that time.
The images suggest four helicopters and 20 lorries were destroyed by fire inside the base, which strategically located in central Syria between war-ravaged Palmyra and Homs.
"The T4 air base was severely damaged by an Islamic State artillery attack. In particular, four Russian Mi-24 attack helicopters appear to have been destroyed," Stratfor said on their website.
The cause of the apparent damage could not be determined from the images obtained by Stratfor.
But the BBC 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.
Tack said there was evidence of "several different sources of explosions across the airport, and it shows that the Russians took a quite a bad hit".
The Stratfor report said that "ordnance impact points are visible" in the images and that a Syrian MiG-25 fighter jet also appeared to have been damaged.
But Russian defence ministry spokesman Igor Konashenkov said: "The burnt air and auto equipment along with many craters from shell detonations have been there for several months.
"This is a result of heavy combat for this aerodrome between Syrian government forces and militants of terrorist groups."
- Russian role key -
Russian news agency RIA Novosti quoted an unnamed Syrian source confirming a "fire" at the base, though he did not specify when it had occurred.
"The reasons of the fire are unknown. It started near the space where four helicopters were located. Fire engines could not access the fire due to shelling by terrorists. The fire spread to the helicopters," the source said, adding that there were no casualties or injuries sustained in the shelling.
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.
"Though the Islamic State failed to cut off the road for any extended amount of time, it did move artillery within range of the base, which it subsequently shelled," Stratfor said in its analysis.
The British-based Observatory also said two days later that continued shelling had caused an explosion at a fuel depot and a fire that destroyed three helicopters.
On May 15, the IS-affiliated Amaq news agency said that four Russian combat helicopters and 20 trucks carrying rockets had been destroyed at the T-4 base by a fire but did not provide further details.
IS seized control of large parts of Syria and Iraq in mid-2014, and the group has claimed deadly attacks in the West and throughout the Middle East.
Russia's intervention has significantly strengthened the Syrian government in a five-year civil war that has killed more than 270,000 people and driven millions from their homes.