There are reports that Israeli warplanes attacked a shipment of Russian missiles inside a Syrian government stronghold, according to a U.S. security official who said the attack took place late Wednesday.
Other reports indicate the airstrike took place at the Syrian port city of Latakia, where a shipment of Russian SA-125 was destroyed.
Israel never confirms airstrikes inside Syria, but an Obama administration official said it took place, without providing details.
Last January, Israeli warplanes took out a Syrian convoy transporting advanced anti-aircraft missiles to Hezbollah, the Lebanese-based Iranian proxy. Israeli officials believe Hezbollah has accrued about 80,000 missiles, some that put all of Israel in range.
Wednesday night's attack took place as Assad met a key deadline in the Russian-backed plan to eliminate his country's chemical weapons stockpile by the middle of next year.
There has been no immediate confirmation from Syria about the attack and the Syrian military has not retaliated.