The New Arab
A Syrian regime airbase deep inside the country's central desert region was likely damaged by Islamic State group saboteurs or an accidental blaze, analysts have said.
It follows a report that suggested Syria's largest air force base, T4, - also sometimes incorrectly described as a "Russian base" - was destroyed by a salvo of Islamic State group Grad missiles in Homs province.
Satellite imagery from Stratfor appears to show that the jihadi group hit the base, between Damascus and Palmyra, with rockets or used explosive devices to destroy a series of helicopters and vehices around a supply depot.
But closer inspection does not indicate craters from rocket impact, analysts have told The New Arab, suggesting an insider attack or accident could be to blame.
Although the missile scenario has not been compeltely dismissed by experts, they believe a more daring commando raid or undercover sabotage effort might have been launched by IS.
Unanswered questions
In mid-May, IS' unofficial news agency Amaq accurately reported that four Russian attack helicopters and 20 trucks loaded with rockets were seen burning inside the T4 airbase "after a fire [broke] out".
Later, Amaq released an image purporting to show its fighters launching Grad missiles at T4 - and claimed the group had destroyed the base.
The Stratfor analyst speaking to the BBC did not believe a fire or accidental explosion could have caused the damage. Instead, he suggested IS was to blame and said the Amaq account appeared to be accurate.
But analysts who spoke to The New Arab disagreed. "I can't see any impact marks - craters etc - and I'm puzzled that there appear to be two different areas of burning," said James Spencer, a MENA political and security analyst.
"Once [IS] saw the report of the fires, IS claimed the hit. They wouldn't be the first to claim credit for an accident."
The destruction of the four choppers, 20 lorries and a seemingly disused jet fighter could have been caused by anything, he said - from a discarded cigarette hitting an oily rag, to deliberate sabotage.
Analysis site Bellingcat has said that T4 has been a prime target for IS, and the militant group has a strong presence in Homs. Due to this threat, the Syrian regime base was temporarily reinforced with L-39 light ground attack aircraft and other helicopters.
The regime has also built up defensive lines at the base and it has now become known as "Fortress T4". But clashes have continued - including one attack upon the officers' mess - making the regime's claim of "impregnability" appear over-confident.
Spencer said the imagery appears to show - even now - that the Russian section of T4 is still lightly fortified and open to attack.
Even heavily guarded bases can fall victim to commando-style militant attacks. This happened in 2012 at the US' Camp Bastion in Afghanistan when the Taliban raided the airbase, Spencer said.
"Air and aviation is a major force multiplier for state forces, so something insurgents are keen to destroy when they get a chance. When they're on the ground, aircraft are vulnerable," he said.
"I'm guessing the perimeter was [a] chain-link fencing with no berm or ditch, so relatively easy to breach."
If the destruction of the choppers were an inside job, Spencer said they might not admit to this to protect the identity of the undercover saboteur.
Commando raid
When news of the attack came out, Russia's ministry of defence was quick to deny that the base had been hit by IS militants, and said that the scorch marks were from an earlier battle with insurgents.
T4 has indeed been the site of sporadic battles between IS and regime fighters. In May 2015, IS claimed an artillery barrage on the site.
On Tuesday, Russian state media quoted an unnamed Syrian regime source saying that a fire destroyed the aircraft, while a mortar barrage from militants stopped firefighters from putting out the blaze.
There was no mention which air forces the Mi-24 attack helicopters belonged to, but they are used by both the Syrian regime and Russia.
Kirill Mikhailov, a Conflict Intelligence Team contributor, believes the aircraft are most likely Russian.
"There is a photo from 21 March of a Russian Mi-24 helicopter at precisely the same position as in the Stratfor satellite imagery, taken by Russian state media," he said.
"The helicopter's camouflage pattern and markings match those used by Russian helicopters in Syria."
The formation of the aircraft match those typical of static Russian helicopters, while choppers have been deployed to "forwarding bases" deep in Syrian territory - including against IS in Homs province - to support regime troops on the ground.
"It must have happened without a significant loss of life as we haven't picked up any traces of the event - such as mourning posts - on Russian social media," he said.
"At this point I would say this is very likely they were Russian helicopters… It is possible there were no Russian fatalities in the event. The [Russian] ministry of defence has been more open about fatalities recently."
Inside knowledge
Mikhailov and the Conflict Intelligence Team have tracked Russian military personnel in Syria and Ukraine, using soldiers' social media posts and satellite images where Moscow's heavy weaponry has been used.
"Given what we have seen with Russian and Ukrainian Grads - not DIY ones - in Donbass [Ukraine], this does not look like a Grad damage pattern," he said.
Yury Barmin, a Russia analyst, believes that explosives could have been planted by an IS saboteur.
"I would say that somebody planted explosive devices rather than IS fired rockets at the base. It also would explain why Russia did not acknowledge the attack," he said.
Barmin also acknowledged that Russia has been more open about military losses in Syria than previously. This could be in part due to Western acceptance of Russia's military role in Syria.
The analyst said that a fire was unlikely to be the cause o fthe destruction, which was most likely caused by an artillery barrage or IS sappers who planted bombs, which could indicate high-level infiltration rather than hi-tech rockets.
Either way, the attack would indicate a serious and embarrassing breach of Russian and Syrian regime security.
"It goes to show how weak security measures are and - or - that there are no radar systems that detect artillery projectiles, which is hard to believe," he said.
"Coupled with IS attacks in Latakia [bombings this week left up to 170 people dead], this definitely calls for a rethink of Russia's strategy in Syria."