Ships in the Strait of Hormuz off the coast of Oman on the 18th [Reuters Yonhap News]

While about 10 oil tankers passed through the Strait of Hormuz after Iran announced its temporary reopening on the 17th (local time), subsequent ship attacks occurred the following day after the Iranian military announced its re-closure.

The UK Maritime Trade Operations (UKMTO) announced on the 18th that it had received a report that a high-speed attack boat associated with the Islamic Revolutionary Guard Corps of Iran had attacked an oil tanker passing through the Strait of Hormuz near Oman.

The UKMTO, citing the tanker's captain, stated that two high-speed attack boats fired without prior wireless warning at a point 20 nautical miles (approximately 37 km) northeast of Oman, and that the ship and its crew were all safe.

The UKMTO also received a report that a container ship was attacked by an unidentified projectile in the sea 25 nautical miles (approximately 46 km) northeast of Oman. Although some containers were damaged by the attack, there were no resulting fires or environmental impacts. There were no immediate reports of casualties.

According to shipping industry sources, some vessels received radio communications from the Iranian navy on the 18th stating, "The Strait of Hormuz is closed again. Ships are not allowed to pass."

Ship tracking firm TankerTrackers.com stated that these vessels were of Indian registry and were attempting to transit the Strait of Hormuz to India but were forced to reroute westward by the Revolutionary Guard, with firing occurring during this process. The firm also added that one of these vessels was an ultra-large crude carrier loaded with 2 million barrels of crude oil.

A radio recording released by the company contained a frantic repetition of the phrase, "Sepah (Revolutionary Guard) Navy, this is oil tanker Sanmar Herald. We have received clearance to pass."

The Indian Ministry of External Affairs announced in a statement on the same day that it had summoned the Iranian ambassador to India to express its deep regret over the firing on Indian-registered vessels and urged the ambassador to convey to the Iranian authorities the demand to resume the existing transit facilitation for ships bound for India.

This armed attack is unexpected, given that ships bound for India have often passed through the strait even after the Iranian military's closure of the Strait of Hormuz.

A high-speed attack boat of the Islamic Revolutionary Guard Corps of Iran [IRGC/EPA Yonhap News]

Although Abbas Araghchi, the Iranian Foreign Minister, announced the temporary lifting of the Strait of Hormuz blockade the previous day, the Iranian military announced the re-imposition of transit controls within a day, citing the U.S. maritime blockade.

Reuters, citing shipping data, reported that at least 12 oil tankers transited the Strait of Hormuz after its re-opening until the reports of attacks.

Ship tracking data shows that vessels passing through the Strait of Hormuz on the 17th and 18th, via the shipping lane near Iran's Larak Island, were predominantly older vessels of non-Western registry, including four sanctioned ships. This route was described as a "coordinated channel" proposed by Iran.

A spokesperson for the Revolutionary Guard stated that Iran had opened the passage to a limited number of oil tankers and merchant ships that had been agreed upon in advance through negotiations.

Other vessels were observed approaching the strait but turned back after the Iranian military announced that it would maintain strict controls, citing the continued U.S. blockade.