The Israeli military said it attacked “dozens” of Iranian targets in neighbouring Syria in response to an Iranian rocket barrage on Israeli positions in the Golan Heights.

The exchanges are the most serious military confrontation between the two bitter enemies to date.

Israel said the 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.

The blistering Israeli assault was by far the most intensive Israeli action in neighbouring Syria since the civil war broke out there in 2011.

Israel has largely tried to stay on the sidelines, 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.

There was no immediate word on Iranian casualties.

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.

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.

In recent months, Israel has warned that it will not accept a permanent Iranian military presence in Syria.

Iran has accused Israel of carrying out a series of deadly strikes on Iranian military positions in Syria in recent weeks, and had vowed retaliation.

Iran has sent thousands of troops to back Syrian President Bashar Assad, and Israel fears that as the fighting nears an end, Iran and tens of thousands of Shiite militiamen will turn their focus to Israel.

Lt. Col. Jonathan Conricus, a military spokesman, said Israel was not looking to escalate the situation. But he said troops will continue to be on “very high alert.”

“Should there be another Iranian attack, we will be prepared for it,” he said.

Iran’s ability to hit back could be limited. Its resources in Syria pale in comparison to the high-tech Israeli military. Iran also could be wary of military entanglement at a time when it is trying to salvage the international nuclear deal.

Israel considers Iran to be its most bitter enemy, citing Iran’s hostile rhetoric, support for anti-Israel militant groups and development of long-range missiles.

US president Donald Trump’s withdrawal from the international nuclear agreement with Iran, with strong support from Israel, has further raised tensions.