The Syrian state news agency SANA, citing initial reports, says Israeli missiles have targeted a military research center near the capital Damascus.
A Syrian activist group, the Britain-based Syrian Observatory for Human Rights, reported large explosions in the area of the Jamraya research center early Sunday.
If confirmed, Sunday's strike would mark the third Israeli attack inside Syria this year. Israel has said it will not allow sophisticated weapons to flow from Syria to the Lebanese militia Hezbollah, an ally of the regime of Syrian President Bashar Assad.
Israeli officials were not immediately available for comment early Sunday.
On Saturday, Israeli officials confirmed that a day earlier Israeli aircraft targeted a weapons shipment apparently bound for Hezbollah.