Israeli strikes that hit several targets in Syria overnight to Monday killed at least 11 pro-regime fighters including two Syrians, a war monitor said.
Israel's military said it had targeted a number of Iranian installations in the country early on Monday, hours after saying it had intercepted a rocket fired from Syrian territory.
The Syrian Observatory for Human Rights (SOHR), a Britain-based monitor, said they were the deadliest Israeli strikes in Syria since May last year.
"Israeli strikes targeting Iranian and Syrian military positions near and south of Damascus killed at least 11 fighters including two Syrians," SOHR chief Rami Abdel Rahman said.
The targets included weapons depots belonging to Lebanese Shia movement Hezbollah and Iranian fighters, he said.
Air strikes and ground-to-ground missiles hit several targets around the capital including near the Damascus airport, as well as near the Thaala military airport to the south of the capital, the Observatory said.
Regime says multiple missiles intercepted
Syrian regime air defences destroyed more than 30 cruise missiles and guided bombs during the Israeli strikes, Russia's defence control centre was quoted by Interfax news agency as saying.
Interfax added that the strikes targeting an airport in southeastern Damascus killed four Syrian regime soldiers and wounded six.
The Russian military also said infrastructure at Damascus International Airport sustained partial damage as a result of the Israeli strikes Sunday and Monday.
Israel confirms air strikes
The Israeli military confirmed in a statement that it attacked Iranian military targets in Syria, hours after carrying out a rare daylight air raid near the Damascus International Airport.
Israel said it was carrying out strikes on Iranian targets in Syria after it intercepted a rocket fired from Syrian territory hours earlier.
It said in a statement that it was "currently striking" the Iranian Revolutionary Guards' Quds Force in Syria and warned Assad's military against "attempting to harm Israeli territory or forces."
It provided no further details on the raids.
Until now Israel has largely refrained from public admissions of its covert military operations in neighbouring Syria, in order to avoid large-scale involvement in the eight-year civil war.
Israeli warplanes have used Lebanon's airspace recently to strike deep inside Syria, including attacking a warehouse near Damascus International Airport earlier this month, according to Syrian regime media.
Israeli Prime Minister Benjamin Netanyahu recently confirmed that Israel has struck hundreds of targets in Syria linked to Iran and Hezbollah, including a weapons facility two weeks ago. Iran and Hezbollah are allied with the Syrian regime in the civil war.