The Syrian regime paid Russia $1 billion for a new air defence system that Damascus says will fend off Israeli air raids, Israeli public broadcaster KAN reported on Saturday.

The Syrian regime paid Russia $1 billion for a new air defence system that Damascus says will deter Israeli air raids, Israeli public broadcaster KAN reported on Saturday.

Citing unnamed sources, the news agency said the payment for the advanced S-300 air defence system has been sitting in Russian banks since a 2013 deal that was held up at Israel's request.

"This will not be a simple challenge for [Israel] and we are dealing with it in different ways and not necessarily through stopping the shipment," a political source was quoted as saying.

The source added the Israeli Prime Minister Binyamin Netanyahu has asked US President Donald Trump for "several special requests regarding the shipment, all of which have all been accepted".

Russia announced earlier this week that it would supply the anti-aircraft missiles after Syrian forces responding to an Israeli air strike mistakenly shot down a Russian military reconnaissance plane, killing all 15 people on board.

The incident sparked regional tensions. Netanyahu called Russian President Vladimir Putin to express sorrow at the loss of life and sent a high-level military delegation to Moscow.

The system replaces Syria's existing Russian-built S-200 system, which dates back to the Soviet era, in a move that had been due to take place in 2013 but was held up by Russia at Israel's request.

In recent years, Israel has carried out around 200 air strikes in war-torn Syria against Iranian targets and what is says are advanced arm deliveries to Lebanese Shia militant group Hizballah.

Iran and Hezbollah are allies of Syrian President Bashar al-Assad in the seven-year civil war.