A tanker sailing through the Strait of Hormuz off the coast of Oman caught fire early on Tuesday after being struck by a projectile, the British military said.
The attack was the latest to target a vessel transiting the narrow entrance to the Persian Gulf, through which around one-fifth of the world's seaborne oil and natural gas trade has traditionally passed during peacetime. Iranian state television said the liquefied natural gas tanker came under attack after ignoring warnings but stopped short of officially claiming responsibility.
Tehran has repeatedly declared that only its designated route through the strait is safe and has been suspected of attacking vessels using an alternative route closer to Oman's coastline.
The United States is keen to resume negotiations with Iran aimed at fully reopening the strait, rolling back Tehran's disputed nuclear programme and securing a permanent end to the war that began on 28 February. However, previous attacks in the waterway have prompted retaliatory US strikes, followed by Iranian attacks on Gulf Arab states, raising the risk of wider regional escalation.
Meanwhile, talks between Washington and Tehran appear to be on hold until after the burial of Iran's late Supreme Leader, Ayatollah Ali Khamenei, who was killed at the start of the war. Reports suggest mourners attending his funeral have increasingly chanted slogans calling for the death of US President Donald Trump.
Authorities flew Khamenei's body overnight to the Shiite seminary city of Qom, where mourners paid their respects on Tuesday.
The United Kingdom Maritime Trade Operations (UKMTO) said the tanker was struck near Limah, Oman, in the Strait of Hormuz. According to the UKMTO, the projectile hit the vessel's port side as it was travelling south through the strait towards the Gulf of Oman.
It said there had been no environmental impact from the strike and that the incident remained under investigation.
Iranian state television, citing anonymous sources, implied that Tehran was behind the attack on what it described as a tanker carrying liquefied natural gas from Qatar. However, the Islamic Republic has made no official claim of responsibility.
Iran's Joint Military Command warned last Thursday that all oil tankers transiting the strait must use routes approved by Tehran. It also warned that any interference by US forces in the waterway "will be met with a rapid and decisive reaction".
However, the Joint Maritime Information Centre, a multinational body overseen by the US Navy, told shipping operators on Monday that the route along Oman's coastline "has been expanded and remains available for all traffic".
Speaking at the White House on Monday, Trump warned Iran that it needed to "make a deal or we're going to finish the job".
"I'd rather make a deal, because I don't want to affect 91 million people," Trump said. "We can knock down their bridges in one hour. We can knock out their energy supply."
Iran and the United States had agreed under an interim arrangement to allow vessels to pass through the strait free of charge for 60 days. However, Tehran insisted it should control shipping routes and later levy transit fees, overturning decades of established practice in the strategic waterway.
The US and many Gulf Arab states have rejected Iran's proposal to charge vessels for passage. Earlier efforts by Oman and a United Nations agency to establish an alternative route near Oman's coast also triggered attacks across the Middle East, underscoring the heightened tensions.
Shipping data firm Kpler reported that at least 108 vessels transited the Strait of Hormuz over the weekend using various routes.
Iranian state television broadcast live aerial footage early on Tuesday showing hundreds of thousands of mourners making their way towards Jamkaran Mosque, south of Qom, for a funeral service for Khamenei. The mosque holds special significance for Shiite Muslims, who believe it was once visited by Muhammad al-Mahdi, the 12th and final Shiite imam, who disappeared in the ninth century and is expected to return one day to establish justice.
Banners and posters bearing images of Khamenei and his son, Iran's new Supreme Leader, Ayatollah Mojtaba Khamenei, were displayed throughout the crowds. Mojtaba Khamenei has yet to appear publicly during the funeral ceremonies, which are taking place over several days. He is believed to be in hiding after reportedly being wounded in the air strike that killed his father.
At the height of the war, before an April ceasefire, Israel targeted senior Iranian officials, in at least one instance reportedly using their public appearances to determine their location. It has also threatened to kill the younger Khamenei.
Authorities have closed roads, restricted airspace and suspended much of daily life during the mourning period, which began on Saturday and will conclude on Thursday when Khamenei is buried at the Imam Reza shrine in Mashhad, his birthplace. Khamenei was 86.