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.
Israel's military has not commented. It periodically attacks what it says are threats to Israeli security in Syria.
These include what it has identified as advanced weaponry destined for the Islamist Lebanese militant group Hezbollah and Iranian bases in Syria.
Israel says it will not allow its arch-enemy Iran to entrench itself in Syria, Iran's key ally.
The facilities hit were linked with Iranian forces, the Syrian Observatory for Human Rights (SOHR), a Britain-based monitoring group, said.
In the Homs area, a research centre and a military airport where Iranian and Hezbollah personnel are based, were targeted, the Observatory said.
Near Damascus, a base hosting the Iranian Revolutionary Guards Corp (IRGC) and a research facility in Jamraya were struck.
IRGC and Hezbollah members were injured in the strikes, the Observatory 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.