Israel has launched one of the heaviest barrages against Iranian targets in neighbouring Syria since the civil war there began in 2011, after Iranian forces in the country bombarded Israeli army bases with rockets.
Israel said its targets included weapons storage, logistics sites and intelligence centres used by elite Iranian forces in Syria. It also said it destroyed several Syrian air-defence systems after coming under heavy fire and that none of its warplanes were hit.
Israeli Prime Minister Benjamin Netanyahu said Israel's air strikes were “appropriate” because Iran had “crossed a red line.”
“We are in the midst of a protracted battle and our policy is clear: We will not allow Iran to entrench itself militarily in Syria,” Mr Netanyahu said in a brief video address.
Israel has largely tried to stay on the sidelines of Syria’s civil war, but has previously acknowledged carrying out over 100 airstrikes over the past seven years, most believed to be aimed at Iranian weapons shipments bound for the Hezbollah militant group.
The confrontation came as expectations of a regional flare-up were stoked by Donald Trump’s announcement he was withdrawing the US from the Iranian nuclear deal.
Israel and Iran have appeared to be on a collision course for months.
In February, Israel shot down what it said was an armed Iranian drone that entered Israeli airspace.
Israel responded by attacking anti-aircraft positions in Syria, and an Israeli warplane was shot down during the battle.
Russia has also sent forces to Syria to back the regime, but Israel and Russia have maintained close communications to prevent their air forces from coming into conflict.
Additional reporting by agencies
Good morning and welcome to live updates from The Independent on the most serious military confrontation between Israel and Iran to date.
The Israeli military said it attacked "dozens" of Iranian targets in neighbouring Syria in response to what it says was an Iranian rocket barrage on Israeli positions in the occupied Golan Heights.
The blistering Israeli assault was by far the most intensive Israeli action in neighboring Syria since the civil war broke out there in 2011 and brings two of the region's major powers to the brink of full-scale war.
Our Middle East reporter, Bethan McKernan, reports on the confrontation here:
Israel and Iran on brink of full-scale war after unprecedented Syria bombardmentIsrael has launched its most intensive attack on Iranian positions in neighbouring Syria since the civil war began in 2011, bringing two of the region's major powers to the brink of full-scale armed conflict. The early morning bombardment came in response to what the Israel Defence Forces (IDF) said was the first ever direct Iranian rocket attack on their troops, in the Golan Heights.
Israel's defence minister, Avigdor Lieberman, has said he hoped the latest round of violence with Iran on the Syrian frontier was over.
"I hope we finished this chapter and everyone got the message," Mr Lieberman said.
He said Israel hit "almost all the Iranian infrastructure in Syria."
He also said none of the Iranian rockets struck inside Israeli-held territory, and they either fell short or were shot down by Israeli defences.
In the Golan Heights, Israeli schoolchildren went to classes as usual on Thursday morning after sirens had sent residents into shelters overnight.
Emmanuel Macron, France's president, has called for a de-escalation of tensions in the Middle East.
"The president has been kept regularly updated. He calls for a de-escalation in the situation," Mr Macron's office said in a statement.
Mr Macron will discuss the Middle East in a meeting with the German chancellor, Angela Merkel, later on Thursday, the Elysee said.
A Syrian war monitoring group has said Israel's attacks on several sites in Syria have killed 23 fighters, including five Syrian soldiers.
The Britain-based Syrian Observatory for Human Rights said the overnight attacks struck several military posts for Syrian troops and Iranian-backed militias near the capital, Damascus, in central Syria and in southern Syria.
The head of the Observatory, Rami Abdurrahman, told the Associated Press five Syrian soldiers, including two officers, and 18 militia fighters were killed.
Mr Abdurrahman said it was not immediately clear if Iranians were among those killed.
He said the toll is likely to rise because some of the wounded are in critical condition.
The Observatory said the strikes targeted suspected locations of the Lebanese Hezbollah group, as well as areas where Iranian advisers are believed to be based.
Russia's defence ministry has said Israel fired more than 70 missiles at Iranian sites in Syria and Syrian air defences shot down more than half of them.
The ministry said 28 Israeli F-15 and F-16 fighter jets launched about 60 air-to-surface missiles during the two-hour raid.
It said Israel also fired over 10 tactical surface-to-surface missiles.
Russia is concerned about growing military tensions between Israel and Iran over Syria and has called for them to de-escalate after recent missile strikes, Russia's deputy foreign minister, Mikhail Bogdanov said.
"This is all very alarming, it causes concern. There should be work to de-escalate the tensions," the TASS news agency quoted Mr Bogdanov as saying.
Israel forewarned Russia of its strikes against multiple targets in Syria, an Israeli military spokesman has said.
"The Russians were informed prior to our attack by the established mechanisms that we have," Lieutenant-Colonel Jonathan Conricus told reporters, without elaborating.
Europe can no longer rely on the US "to protect it," Angela Merkel has said, after Donald Trump signalled he would pull out of the Iran nuclear deal.
In 2018 Syria’s war appears to have entered a new chapter, our Middle East reporter, Bethan McKernan writes.
Tensions between Iran and Israel over the presence of Iranian troops and allied Hezbollah, which fight alongside president Assad, have been building for a while, but with the wars against both Isis and the rebels all but won, it seems like this front is now hotting up.
There has been a series of events leading up to the current escalation: in February, Israel accused Iran of sending an armed drone into its territory.
Israel retaliated with strikes on Iranian positions, but in the process an F-16 jet was shot down, the first such Israeli loss in 36 years. Syria, Iran and Hezbollah seized on it as a huge symbolic victory.
Israeli strikes have grown fiercer since, killing at least 13 Iranian nationals in Syria.
Tehran has vowed the attacks won’t go unpunished but its military capabilities are limited. It also needs the goodwill of the international community as it struggles to save the 2015 nuclear deal, which lifted crippling sanctions.
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