The two tankers were set ablaze near Iraq’s southern port of Basra, forcing a pause of operations at the country’s oil terminals.
The Iraqi News Agency, citing a military official, reports that 38 crew members were rescued and one person died.
Iran’s official news agency IRNA said the Islamic Revolutionary Guard Corps (IRGC) struck one of the two ships – a US-owned vessel, the Safesea Vishnu – because it had ignored warnings and failed to comply with orders.
Indian authorities earlier said the Safesea Vishnu, which sails under the Marshall Islands flag, was attacked by an unmanned speed boat.
A second vessel, Greek-owned and Maltese-flagged Zefyros, was struck while it was in the middle of a ship-to-ship transfer with the Safesea Vishnu, the vessel’s manager Benetech Shipping said.
Separately, a Chinese-owned container ship of the coast of the United Arab Emirates (UAE) was “struck by an unknown projectile causing a small fire onboard”, the UK Maritime Trade Operations (UKMTO) Centre said.
The cause of the latter two strikes is still being investigated.
About 20% of the world’s oil usually passes through the Strait of Hormuz and the war has sent global oil prices soaring – reaching $100 a barrel at one point.
“Get ready for the oil barrel to be at $200 because the oil price depends on the regional security which you have destabilised,” Ebrahim Zolfaqari, spokesperson for Iran’s military command said.
On Wednesday, President Donald Trump insisted fluctuations in prices were a “matter of war” and “prices are coming down very substantially”.