Four civilians were killed and 21 injured in Israeli missile strikes near the Syrian cities of Damascus and Homs, Syrian state media said.
The Syrian military responded to missiles launched by Israeli warplanes, the Sana news agency said.
Israeli jets targeted military bases from Lebanese airspace at around midnight on Sunday, it reported.
A number of the missiles were intercepted by Syrian air defences, Sana added.
Israel's military declined to comment on the report.
The facilities hit were linked with Iranian forces, the Syrian Observatory for Human Rights (SOHR), a Britain-based monitor, said.
In the Homs area, a research centre and a military airport where Iranians and the Hezbollah Shia movement are based, were targeted, the Observatory said.
Near Damascus, a base hosting the Iranian Revolutionary Guards (IRGC) and a research facility in Jamraya were struck.
Some personnel from these forces were injured, Rami Abdel Rahman, SOHR's chief, said.
In Sahnaya, south of Damascus, four civilians - including a toddler - were killed as a result of Israeli "aggression", Syrian state-run broadcaster al-Ikhbariya said.
Israel has carried out dozens of strikes in Syria since civil war broke out in the country in 2011. It sees the presence of Iran and Hezbollah in Syria as a security threat.
Iran, Israel's arch-enemy, has sent thousands of military personnel to support Syria's President Bashar al-Assad in the country's civil war.
Hezbollah, an Islamist political party and militant group based in Lebanon, is also supporting the Syrian president.