By Dan Williams

JERUSALEM (Reuters) -Iran launched dozens of drones at Israel on Saturday but they will take hours to reach their targets, Israel’s military said, an attack that may trigger a major escalation between the regional archenemies, with the U.S. pledging to back Israel.

Two security sources in Iraq said dozens of drones had been spotted flying from Iran toward Israel over Iraqi airspace in what Iranian Press TV called “extensive drone strikes” by the Revolutionary Guards.

Iran has vowed retaliation for what it called an Israeli strike on its Damascus consulate on April 1 that killed seven Revolutionary Guards officers including two senior commanders. Israel has neither confirmed nor denied responsibility for the attack.

U.S. President Joe Biden, who on Friday warned Iran against attacking Israel after saying such a scenario appeared imminent, has pledged to stand with Israel against Iran, the White House said.

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.

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.

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.