Reports say Israeli warplanes have struck inside Syria, although Tel Aviv has refused to confirm any strike.
Reports on October 31 said Israeli warplanes had targeted a military base near the port city of Latakia.
Syrian opposition forces said the base had stored Russian-made missiles.
CNN quoted an unidentified U.S. official as saying Israel believed the missiles might be transferred to its Lebanese militia enemy Hizballah.
The Syrian Observatory for Human Rights said late on October 30 that there had been an explosion at an air base near Latakia.
The Lebanese military said six Israeli jets had flown over Lebanese territory on October 30.
An Israeli Defense Ministry spokesman refused to comment on the reports.
It would not be the first Israeli military strike inside Syria.
Israel struck Syrian targets near Damascus in January and twice in May. Tel Aviv was also suspected of having destroyed a naval installation near Latakia in July.
Meanwhile, U.S. Secretary of State John Kerry has welcomed news that Syria has destroyed or rendered inoperable all of its declared chemical weapons production and mixing facilities.
Earlier on October 31, the Organization for the Prohibition of Chemical Weapons (OPCW), said Syria had met a November 1 deadline to carry out the task.
In a statement, Kerry said it was now important to "make sure the job is finished and that everyone of these banned weapons is removed and destroyed."
Under a deal brokered by Kerry and Russian Foreign Minister Sergei Lavrov, Damascus agreed to destroy all its chemical weapons after Washington threatened to use force in response to the killing of hundreds of people in a sarin attack on the outskirts of Damascus on August 21.
Syria is now facing a fresh deadline of November 15, when it and the OPCW must agree to a detailed plan of destruction, including how and where to destroy more than 1,000 metric tonnes of toxic agents and munitions.
Based on AP and Reuters reporting