Iran’s Islamic Revolutionary Guards Corps said it launched dozens of drones and missiles at Israel on Saturday (local time), an attack that may trigger a major escalation between the regional archenemies.

Israel’s military said the drones, which Iraqi security sources said were seen flying over the country from Iran, would take hours to reach their targets.

Israeli Channel 12 said missiles Iran had launched would likely strike sooner but that some missiles and drones had been shot down over Syria or Jordan.

Iran has vowed retaliation for what it called an Israeli strike on its Damascus consulate on April 1 that killed seven guards officers including two senior commanders and said its strike was a punishment for “Israeli crimes”.

Israel has neither confirmed nor denied responsibility for the consulate attack.

United States President Joe Biden, who on Saturday (AEDT) warned Iran against attacking Israel after saying such a scenario appeared imminent, has pledged to stand with Israel against Iran, the White House said.

British Prime Minister Rishi Sunak condemned Iran’s “reckless” attack against Israel, which he said showed that it was “intent on sowing chaos in its own backyard”.

“These strikes risk inflaming tensions and destabilising the region. Iran has once again demonstrated that it is intent on sowing chaos in its own backyard,” Sunak said in a statement.

While Egypt called for “utmost restraint” to spare the region and its people from further instability and tension.

A retired Israeli general, Amos Yadlin, told the country’s Channel 12 news that the Iranian drones were equipped with 20 kg (44 pounds) of explosives each.

Israel’s military said sirens would sound in any threatened areas and that its defences were poised to deal with them.

Israel and neighbouring Jordan, which lies between Iraq and Israel, said they were closing their airspace on Saturday night and Jordan announced a state of emergency.

Syria, an ally of Iran, was putting its ground-to-air defence systems around the capital and major bases on high alert, army sources there said.

The Gaza war between Israel and Hamas, now in its seventh month, has driven up tensions in the region, spreading to fronts with Lebanon and Syria and drawing long-range fire at Israeli targets from as far away as Yemen and Iraq.

Those clashes now threaten to morph into a direct open conflict pitting Iran and its regional allies against Israel and its main supporter the US.

Earlier on Saturday, Iran’s state-run IRNA news agency reported that a guards helicopter had boarded and taken into Iranian waters the Portuguese-flagged MSC Aries.

MSC, which operates the Aries, confirmed that Iran had seized the ship and said it was working “with the relevant authorities” for its safe return and the wellbeing of its 25 crew.

MSC leases the Aries from Gortal Shipping, an affiliate of Zodiac Maritime, Zodiac said in a statement, adding that MSC is responsible for all the vessel’s activities. Zodiac is partly owned by Israeli businessman Eyal Ofer.

Israeli Foreign Minister Israel Katz accused Iran of piracy.