Israel's Prime Minister Benjamin Netanyahu has ordered his cabinet to stay silent on the issue of Russian missile deliveries to Syria, public radio said on Wednesday.

His remarks came after several ministers criticised Moscow's arms deals with Damascus and raised the possibility of an Israeli response should the Jewish state feel under threat.

Defence Minister Moshe Yaalon on Tuesday warned Israel would "know what to do" if Russia delivered promised anti-aircraft missiles to the regime of Syrian President Bashar al-Assad.

"The deliveries have not taken place, and I hope they do not. But if, by misfortune, they arrive in Syria, we will know what to do," Yaalon told reporters.

Israel has launched several air raids inside Syria this year, targeting convoys transporting weapons to its arch foe Hezbollah in Lebanon.

Intelligence and Strategic Affairs Minister Yuval Steinitz also confirmed Israel would "react to any threat".

"I hope Damascus understands that. We will react forcefully," he told reporters on Tuesday, describing Russia's planned delivery of the S-300 anti-aircraft missiles as "morally wrong".

Earlier this month, Justice Minister Tzipi Livni also criticised Russia's arms deals with Syria, where a two-year conflict that started as an anti-regime uprising has killed more than 90,000 people.

Moscow on Tuesday defended its arms shipments to Damascus.

Deputy Foreign Minister Sergei Ryabkov said the missiles were a "stabilising factor" which could act as a deterrent against foreign intervention, as fears grow that the violence could spill over into neighbouring countries.