Three ships passing through the Strait of Hormuz have been attacked in recent days, British maritime officials said.
The ships were struck by unknown projectiles, resulting in two casualties, according to the United Kingdom Maritime Trade Operations agency.
INTERCARGO, an association of cargo shipowners, reported that a sailor aboard the Liberian-flagged bulk carrier Minoan Dynasty was killed on Monday.
While hostilities between Iran and the United States have eased in recent weeks, a string of attacks on vessels passing through the strait has unsettled investors, pushing oil prices to a three-week high.
Brent crude futures jumped more than 3 per cent over the past week, to $US91.38 by 5:45pm AEST on Friday.
The narrow waterway between Iran and Oman is a vital shipping route for oil in the region.
Iran's top negotiator, Mohammad Baqer Qalibaf, said on state media yesterday the strait will remain shut until the US meets the conditions of an interim deal signed between the two countries in June.
The conditions include the US lifting its own blockade, removing oil sanctions, unfreezing Iranian assets and ending military threats, he told parliament.
However, last week, Saudi Aramco, the world's top oil producer, resumed loading oil from inside the strait, eyeing Singapore and Malaysia as potential destinations.
Despite Iran and the US not directly trading blows, energy prices have remained higher than pre-war levels while the roughly 500 million barrels that usually flow through the strait each month slowed to a trickle.
In a rally speech on Friday, US President Donald Trump said Americans should prepare for higher petrol prices as the war continues.
Shipping through the contested strait has slowed further in recent days, following similar attacks on vessels last week and talks between Iran and the US stalling.
Mr Trump said there are no talks planned between the two countries, and insisted the strait was open.
"The Hormuz Strait is open and operating. All water mines have been removed or detonated," he said on Truth Social yesterday.
A ceasefire between Iran and the US expired on Monday, and Mr Trump said he would not be extending it.
The president also said that the US would claim the strait as a US territory after the war.
The strait is becoming a point of stress for the American president, as the ongoing Iran war becomes increasingly unpopular at home.
He recently threatened to bomb US ally Oman, saying: "If Oman gets in the way, we'll bomb the shit out of them", in an interview with Fox News.
Oman, whose coastline is a part of the Strait of Hormuz, and Iran have been discussing opening the strait for weeks.
Six months into the conflict, 17 seafarers have died in the waterway according to the UN, with the number of ships passing through estimated to have dropped by roughly 90 per cent.
Many ships travel with their navigation and identification devices turned off to make them harder to attack.
"Seafarers are civilians and must never become targets or collateral victims of geopolitical conflicts," INTERCARGO said in a statement.
