Israeli missile strikes targeted Iranian military positions in the Syrian provinces of Hama and Tartus on Tuesday, the Syrian Observatory for Human Rights monitoring group said.
Syria's state news agency SANA said its air defence systems downed several missiles launched from Israeli warplanes.
The Observatory said missiles struck Wadi Al Oyoun in the central province of Hama, near a scientific research centre which was already targeted by Israeli strikes in July and last year.
Iranian military positions in coastal region of Banias, in the province of Tartus, were also targeted, the Britain-based monitoring organisation said.
"There was material damage," said Observatory chief Rami Abdel Rahman.
"The air defence system responded to an Israeli aggression carried out by aircraft... that targeted some of our military positions in the provinces of Tartus and Hama," SANA said, quoting a military source.
"Some of the missiles" were downed, the agency said, reporting an initial casualty toll of one dead and four wounded.
The Observatory said several explosions had been heard in the areas around Masyaf and Wadi Al Uyoun near Hama city, areas where there are Iranian military facilities.
Mr Abderahman said the attack had also targeted around the coastal city of Baniyas for the first time, with two rockets hitting around one kilometre from an oil refinery.
An Israeli military spokeswoman declined to comment on the report.
Syrian state television said air defences downed five rockets.
SANA said the planes had come at a low altitude from west of neighbouring Lebanon's coastal capital Beirut.
Reuters journalists in Beirut heard unusually loud aircraft sounds shortly before the strikes were reported in Syrian media.
Lebanon's Al Mayadeen news said Israeli fighter planes released countermeasures against anti-aircraft fire "and withdrew towards the sea at the same time as the sounds of explosions were heard in Hama countryside."