Syria's capital Damascus was rocked by explosions early Sunday.
Syrian state-run media said Israeli rockets had struck a military research center on the outskirts of the capital.
The blasts occurred a day after an Israeli official said his country had carried out an air strike targeting a consignment of missiles in Syria. The research center in Jamraya hit Sunday was also targeted by Israel in January.
Earlier, activists in Syria said thousands of Sunni Muslims have fled the coastal city of Banias, fearing attacks after the alleged mass killings at a nearby village.
The Britain-based Syria Observatory for Human Rights estimated that 4,000 Sunnis fled their homes early Saturday. An observatory official told VOA pro-government security forces are instigating the exodus.
The observatory has accused Syrian forces of killing at least 150 civilians, including women and children, in a "large-scale massacre" in the northwest village of Bayda on Thursday.
Bayda is mainly inhabited by Sunni Muslims who dominate the country's rebel movement.
On Saturday, the U.S. State Department condemned the "atrocities" committed in Bayda. A spokesperson said the U.S. is "appalled by horrific reports" of the many civilians killed in the attack.
Rights groups have accused government and rebel forces of committing war crimes during the Syrian conflict, which has killed at least 70,000 people.