Iranian gunboats fired on a tanker in the Strait of Hormuz on Saturday, a British maritime security agency reported, after Iran's military reversed a pledge to open the route to shipping.
The tanker's captain reported being approached 37 kilometres (23 miles) northeast of Oman by two gunboats of Iran's Revolutionary Guards Corp (IRGC). Without any radio warning, the gunboats "then fired upon the tanker," the UK Maritime Trade Operations Centre said in an online statement.
"Tanker and crew are reported safe. Authorities are investigating," the statement added.
Meanwhile, two Indian vessels reversed course in the strait, following reports of gunfire from Iran's Revolutionary Guard, a vessel-tracker said.
TankerTrackers.com said the vessels include an Indian-flagged super tanker, carrying 2 million barrels of Iraqi oil.
The incidents came shortly after Iran's Supreme Leader, Mojtaba Khamenei, in a statement, warned that Tehran's Navy was ready to defeat US forces in the Strait of Hormuz.
In a statement carried on his Telegram channel, Khamenei, who has not been seen in public since before the start of the war, said Iran's "brave navy stands ready to make the enemies taste the bitterness of new defeats."
Earlier in the day, Iran's central military command announced that it would resume "strict management" of the strait, calling the decision a response to a continued US blockade of Iranian ports.
In a statement shared on state television, the military stated that Washington had broken a promise by continuing its naval blockade of ships sailing to and from Iran's ports.
The announcement came as maritime tracking sites showed several ships making a dash through the narrow waterway, hugging close to Iranian territorial waters as instructed by Tehran and, for some, broadcasting their identity as Indian or Chinese in an apparent attempt to show their neutrality.
Tehran had on Friday declared the strait, which usually carries a fifth of the world's oil and liquefied natural gas, open after a ceasefire was agreed in Lebanon to halt Israel's war with Hezbollah.
The decision was reversed after US President Donald Trump on Saturday said that he was planning to maintain the naval blockade of Iranian ports until both the countries agree on a permanent ceasefire deal. He also hinted that the temporary ceasefire agreement between Iran and the US, which is due to expire on April 22, would noty be extended.
"Maybe I won't extend it, but the blockade is going to remain," Trump told reporters aboard Air Force One, when asked if the ceasefire will be extended.
Asked about a potential deal, Trump said, "I think it's going to happen."
Confusion over the critical chokepoint threatened to deepen the energy crisis roiling the global economy and push the two countries toward renewed conflict, even as mediators expressed confidence a new deal was within reach.
(With inputs from AP, AFP)