Large explosions are being reported in the Mount Qassioun area of the Syrian capital, Damascus.
Syrian state TV says an Israeli military rocket has hit a military research centre.
Mount Qassioun is the site of military installations that have been used to shell rebel-controlled areas.
On Friday, Israeli planes launched a strike inside Syria targeting a shipment of arms destined for Lebanon's Hezbollah.
Syrian forces and rebels have been fighting around Damascus for months but with neither side gaining the upper hand.