Syria says Israeli jets have hit a military base in the west of the country, amid reports of a strike on a chemical weapons factory.
An army statement said rockets fired from Lebanese airspace targeted the site near Masyaf, killing two soldiers.
Unconfirmed Arab media reports say a chemical weapons production facility was hit in the attack.
Israel, which has carried out clandestine attacks on weapons sites in Syria before, has not commented.
The incident comes a day after UN investigators said they had concluded that the Syrian government was behind a deadly chemical weapons attack on a rebel-held town in April.
At least 83 people died in the attack on Khan Sheikhoun, the UN says. Damascus has always denied using chemical weapons.
Western intelligence reports say Syria is continuing to produce chemical weapons, including at Masayaf, in violation of a 2013 deal to eliminate them.
Israel has sporadically carried out air strikes on sites in Syria in recent years.
It recently accused Syria of allowing its arch-enemy Iran to build missile factories there and says it aims to thwart the transfer of advanced weaponry from Syria to the Lebanese militant group Hezbollah.