Three Indian sailors were missing on Wednesday after US forces struck their oil tanker in the Gulf of Oman.
The MT Settebello was the second oil tanker to be hit by the US military in two days as part of its blockade of Iranian ports.
India's Foreign Ministry said 24 of its citizens had been on board. It said 21 had been rescued but three remained missing as Oman led a search-and-rescue operation.
The US Central Command said the Palau-flagged ship was attempting to transport oil from Iran, when it was hit at 11.14pm on Tuesday. A US warplane “fired precision munitions into the ship’s engine room after the crew repeatedly failed to comply with directions”, it said.
A fire was reported on board. India said its embassy in Muscat was helping Omani authorities with the search-and-rescue operation.
On Monday, a US fighter jet attacked the MT Marivex, an unladen oil tanker, in the Gulf of Oman. Like the MT Settebello, it had a crew of 24 Indian seafarers. They were all declared safe.
The MT Settebello is the eighth ship to be attacked by US forces since they began their blockade of Iranian ports in mid-April. The blockade was ordered by President Donald Trump to counter Iran's closure of the Strait of Hormuz.
The latest strikes come as the US, Israel and Iran exchange some of their heaviest blows since the early weeks of the conflict, raising fears of a return to full-scale war.
The latest spiral of attacks began when Israel attacked Beirut on Sunday, defying warnings from Iran that it would not tolerate the situation in Lebanon.
Iran then launched its first direct attacks on Israel since April, leading to retaliation from Israel. Those attacks ended on Monday, but were followed by retaliatory fire between the US and Iran after an American helicopter was shot down.
The head of the International Maritime Organisation, Arsenio Dominguez, condemned the latest attack on the oil tanker. “This is simply unacceptable. My thoughts are with the families of the three missing seafarers,” he said.
The eight ships 'disabled' by US forces during blockade
The US military says it had "disabled" eight ships for breaching its blockade of Iranian ports. They are:
April 19: Iranian cargo ship MV Touska is attacked by a US destroyer and later boarded by marines. The crew of 22 is returned home through Pakistan.
May 6: An unladen oil tanker, MT Hasna, has its rudder struck by a fighter jet after the US Central Command said it was breaching the blockade.
May 8: Two oil tankers are attacked while allegedly en route to Iran. The MT Sea Star III and MT Sevda have munitions fired into their smokestacks from a US fighter jet.
May 29: A US warplane launches a Hellfire missile at the Gambia-flagged MV Lian Star after what the US Central Command said were 20 warnings not to sail to Iran.
June 2: The MT Lexie, an oil tanker, is also hit with a Hellfire missile on its way to the oil-producing Kharg Island, US forces say.
June 8: A US Super Hornet fighter jet fires on the Palau-flagged MT Marivex, which the US Central Command said was heading towards Iran.
June 9: The MT Settebello has munitions fired into its engine room while allegedly ‘attempting to transport oil from Iran’. Three Indian sailors are reported missing.
