Russia is sending troops, weapons, fighter planes and now an advanced anti-aircraft missile system to Syria according to a Russian source and two Western officials on Friday.
They say the move is part of Russia stepping up its support of Syrian President Bashar al-Assad, who has faced a string of military losses in recent months.
The Western officials said the advanced SA-22 system would be operated by Russian military personnel and not Syrians, though this is largely due to the training required to operate the sophisticated system..
"This system is the advanced version used by Russia and it's meant to be operated by Russians in Syria," said a Western diplomat who receives regularly briefing on Israeli, U.S. and other intelligence assessments as part of his duties.
A U.S. official also confirmed the information about the missile system shipment, which according to Russian sources is the second time Russia has sent the SA-22 system, known in Russia as Pantsir-S1, to Syria. The first shipment was in 2013.
Syrian officials have yet to comment.
The U.S., European and regional allies, which have been leading air strikes over Syrian airspace in attacks on ISIS and other extremist Islamic terror groups, are now concerned about the introduction of advanced anti aircraft weapons, the diplomat said.
Although Russian Foreign Minister Sergei Lavrov said Russia was sending military equipment to Syria to help the Assad government combat Islamic State fighters, experts says the sending of anti-aircraft missiles would not support that claim as neither Islamic State nor Syrian rebel groups have any aircraft.
Even if Russian troops controlled and operated the missiles system, the fact it was in Syria is of concern to Israel, which in the past has bombed sophisticated arms it suspected were in the hands of Hezbollah, Assad's Lebanese guerrilla allies.
The diplomatic source said "In the Middle East you never know what will happen. If the Russians end up handing it the SA-22 over to the Syrian military, I don't think the Israelis would intervene but they would go bananas if they see it heading towards Hezbollah in Lebanon."
An Israeli military spokesman, although not commenting on the missile system shipment, said the country would continue its policy of stopping advanced weapons reaching Hezbollah.
"We have open relations with the Russians who have come to save Assad in the civil war. Along with this, we will not allow our sovereignty to be compromised or the transfer of advanced or chemical weapons (to Hezbollah). We are following the developments and keeping open channels with Moscow."