Israeli warplanes fired missiles at military sites in Homs and the Damascus outskirts, killing at least four civilians and wounding another 21, Syrian state television said on Monday.
Syrian air defences confronted the attack, which was launched from Lebanese airspace, the Syrian Defence Ministry said on its Telegram feed.
"We don't comment on such reports," an Israeli military spokeswoman said.
Syrian state-run broadcaster Al Ikhbariya said the four civilians including a baby were killed in Sahnaya, south of Damascus, as "a result of the Zionist aggression".
State news agency SANA also reported that Syrian air defences brought down a number of the missiles.
"Our air defences confronted enemy missiles launched by Israeli warplanes towards some of our positions in Homs and in the vicinity of Damascus," a military source said.
The Syrian Observatory for Human Rights said from Britain that the strikes had been aimed at a research centre and a military airport west of the city of Homs, where Lebanese militia Hezbollah and Iranians were posted.
Rami Abdulrahman, the observatory chief, said the strikes injured some of these forces.
The targets near Damascus were still unclear.
Israel has carried out hundreds of air strikes in Syria since the start of the conflict in 2011, aiming for forces loyal to President Bashar Al Assad and the regime's allies, Iran and Hezbollah.
