The Israeli military said its jets have struck a series of Iranian military targets in Syria.
The announcement is a rare departure from Israel’s years-long policy of ambiguity regarding activities in neighbouring war-torn Syria.
The targets included munition storage facilities, an intelligence site and a military training camp, the military said.
The strikes were in response to a surface-to-surface rocket that Iranian forces fired towards Israel on Sunday which was intercepted by Israel’s Iron Dome missile defence system over a ski resort in the Golan Heights.
That followed a rare Israeli daylight air raid near Damascus International Airport.
The Britain-based Syrian Observatory for Human Rights said Monday’s pre-dawn strikes lasted for nearly an hour and were the most intense Israeli attacks since May.
It said 11 people were killed in the strikes.
The Russian military said four Syrian troops were among those killed in air strikes that targeted three different locations and damaged unspecified infrastructure at Damascus airport.
Israeli military spokesman Lt Col Jonathan Conricus said the Iranian missile attack that prompted the strong Israeli response was “premeditated”.
Iranian forces in Syria fired the mid-range surface-to-surface missile towards Israel from the Damascus area – a missile he said had been smuggled into Syria specifically for that purpose.
Lt Col Conricus declined to further identify the type of missile but said it had not been used in any of the internal fighting of the civil war and had “no business” being in Syria.
In Iran, the chief of Iran’s air force, General Aziz Nassirzadeh, said his forces are “impatient and ready for a fight against the Zionist regime to wipe it off the Earth”, according to a news website affiliated with Iran’s state television, YJC.ir.
Iranian officials have repeatedly threatened to annihilate Israel.
Israel has only recently acknowledged carrying out hundreds of strikes against Iranian and Hezbollah targets in Syria in recent years.
It previously typically offered only general warnings against allowing Iran to establish a military foothold in Syria and refrained from commenting directly for fear of triggering a reaction and being drawn into the deadly fighting.
Israeli political and military leaders have been far more verbose of late, and Monday’s announcement went a step further, reporting the strikes in real time and detailing the targets.
Lt Col Conricus would not confirm whether the measures marked an official abandonment of the policy of ambiguity, merely saying that it was a “retaliatory strike against active aggression by Iran”.
He said Israel had sent warnings to Syria ahead of the attack to refrain from attacking Israeli warplanes, but that Syria ignored those warnings and fired anti-aircraft missiles.
He said Israel responded by destroying Syrian anti-aircraft batteries.
The Russian military said that the Syrian air defences shot down more than 30 Israeli cruise missiles, a claim that was doubted in Israel.
The military said the Mount Hermon ski site has been closed.
Israel holds Syria responsible for allowing the Iranian forces to use Syrian territory as a base of operations against Israel.
Israeli President Reuven Rivlin said the Iranian rocket attack provided “live testimony” to Iran’s entrenchment in Syria that could plunge the entire Middle East into war.