Iranian forces based in Syria fired 20 rockets at Israeli front-line military positions in the Golan Heights early on Thursday, the Israeli military said.
The attack triggered an Israeli reprisal and escalating already heightened tensions in the area.
The Israeli military said its Iron Dome rocket defence system intercepted some of the incoming projectiles, while others caused only minimal damage.
Syria’s capital of Damascus shook with sounds of explosions just before dawn, and firing by Syrian air defences over the city was heard throughout the night.
An Israeli official said Israel was targeting Iranian positions inside Syria, while Syria’s state news agency SANA quoted a Syrian military official as saying Israeli missiles hit air defence positions, radar stations and a weapons warehouse, but claiming most incoming rockets were intercepted.
The Israeli newspaper Haaretz quoted an unidentified security official as saying Israel’s attacks inside Syria were the most extensive since the two nations signed a disengagement agreement after the October war of 1973.
Lieutenant Colonel Jonathan Conricus, an Israeli military spokesman, said earlier that Iran’s Al Quds force fired the rockets at several Israeli bases, though he would not say how Israel determined the Iranian involvement.
The incoming attack set off air raid sirens in the Israeli-controlled Golan, which was captured from Syria in the 1967 war.
Israel “views this Iranian attack very severely,” he told reporters.
Syria’s state media said Syrian air defences intercepted “hostile Israeli missiles” early on Thursday that were fired over southwestern Damascus.
Hours later, state-run Al-Ikhbariya TV broadcast a live feed of Syrian air defences firing into the sky above the capital, and loud explosions and air defence firing were heard through the night.
An Israeli army spokesman, Avichay Adraee, said on Twitter that Israel was “acting against Iranian targets inside Syria,” a rare admission by an Israeli official.
Israel has been on heightened alert in recent days, anticipating an Iranian attack following Iranian vows to retaliate to what it says are recent Israeli strikes in Syria targeting Iranian outposts.
Late on Tuesday, Syrian state media said Israel struck a military outpost near the capital of Damascus.
The Britain-based Syrian Observatory for Human Rights said the missiles targeted depots and rocket launchers that likely belonged to Iran’s elite Revolutionary Guard, killing at least 15 people, eight of them Iranians.
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Last month, an attack on Syria’s T4 air base in Homs province killed seven Iranian military personnel. On April 30, Israel was said to have struck government outposts in northern Syria, killing more than a dozen pro-government fighters, many of them Iranians.
Israel has neither confirmed nor denied most of the airstrikes. But for months, it has repeatedly said it will not accept a permanent Iranian military presence in Syria.
Iranian forces moved into Syria after the outbreak of the Syrian civil war in 2011 to back the forces of President Bashar Assad.
As that war winds down, and Assad appears to be headed toward victory, Israel fears that Iran, along with tens of thousands of Iranian-backed Shiite militiamen, will carry out attacks against Israel.
US president Donald Trump’s announcement on Tuesday that the US was withdrawing from the 2015 nuclear deal with Iran has triggered uncertainty and threatened to spark more unrest in the Middle East.