Moscow is sending an advanced anti-aircraft missile system to Syria, two Western officials and a Russian source told Reuters, as part of what the West believes is stepped-up military support for embattled President Bashar al-Assad.
This occurs as RAAF F/A-18 Hornets based in the Middle east commenced operations against ISIS across the Syrian border last week. ISIS forces both in Syria and Iraq are not using aircraft in their fight against the Assad regime or the Iraqi forces and the Russian intentions for the use of the system are unclear.
The Western officials said the SA-22 system would be operated by Russian troops, rather than Syrians. The system was on its way to Syria but had not yet arrived.
"This system is the advanced version used by Russia and it's meant to be operated by Russians in Syria," said one of the sources, a Western diplomat who is regularly briefed on US, Israeli and other intelligence assessments.
Two US officials separately confirmed the information with one saying the system may be part of a Russian effort to bolster defences at the airfield.
The Russian source, who is close to the Russian navy, said the delivery would not be the first time Moscow had sent the SA-22 system, known as Pantsir-S1 in Russian, to Syria. It had been sent in 2013, the source said.
"There are plans now to send a new set," the source said, without detailing how far along the process was.
The US has been leading a campaign of air strikes in Syrian air space for a year, joined by aircraft from European and regional allies including Britain, France, Jordan and Turkey and Australia. US forces operating in the area are concerned about the potential introduction of the weapon, the diplomat said.
US officials say they believe Moscow has been sending troops and equipment to Syria, although they say Russia's intentions are not clear.
Lebanese sources have told Reuters that Russian troops have begun participating in combat operations on behalf of the Assad government. Moscow has not commented on those reports. DEBKA file reported last week that Iranian marines assisting the Assad regime had joined up with Russian marines who had already established a base near the port town of Latakia.
Speaking at a news conference in Moscow, Russian Foreign Minister Sergei Lavrov said Russia was sending military equipment to Syria to help the Assad government combat Islamic State fighters, and had sent experts to help train the Syrian army to use it.
However, the dispatch of advanced anti-aircraft missiles would appear to undermine that justification, since neither Islamic State nor any other Syrian rebel group possesses any aircraft.
Lavrov also said coordination was needed between Russia's military and the Pentagon to avoid "unintended incidents" around Syria. Russia was conducting pre-planned naval drills in the eastern Mediterranean, he said.
RAAF Hornet strike jets are on course to hit Islamic State training camps and command centres in Syria during cross border bombing missions from Iraq. Minister for Defence Kevin Andrews stressed that Australian jets and their young pilots will be out of harm's way from any Syrian anti-aircraft weapons attack. He discussed how the Syrian military are in the western part of the country as opposed to being near ISIS-dominated regions.