An "unknown projectile" struck a tanker in the Strait of Hormuz this week, causing a fire that has since been put out, a British maritime agency said early on Thursday.
Iran has effectively blockaded the Strait of Hormuz since the United States and Israel attacked the republic in late February.
Tehran wants to charge tolls for passage, and has attacked ships it accuses of trying to skirt its preferred route.
"Local authorities have reported a tanker has been hit by an unknown projectile causing fire to the vessel which has since been extinguished," the United Kingdom Maritime Trade Operations (UKMTO) said.
The incident occurred near the Omani coastal city of Khasab and was reported to the UKMTO on Tuesday, the agency said.
There were no casualties among the crew and no adverse environmental impact, it said.
Authorities are investigating the cause, it added.
The online notice did not specify the vessel's nationality or direction of travel.
US Treasury Secretary Scott Bessent laid out plans on Monday for the "economic asphyxiation" of Iran.
Iranian President Masoud Pezeshkian said on Wednesday that the new sanctions "will not achieve anything".
