Two rockets struck an Iranian tanker travelling through the Red Sea off the coast of Saudi Arabia on Friday, Iranian officials said.
It is the latest incident in the region amid months of heightened tensions between Tehran and the US.
There was no word from Saudi Arabia on the reported attack and Saudi officials did not immediately respond to requests for comment.
Iranian state television said the explosion damaged two storerooms aboard the unnamed oil tanker and caused an oil leak into the Red Sea near the Saudi port city of Jiddah.
The state-run Irna news agency, quoting Iran's National Iranian Tanker Co, identified the stricken vessel as the Sabity.
That vessel last turned on its tracking devices in August near the Iranian port city of Bandar Abbas.
Lieutenant Pete Pagano, a spokesman for the US Navy's Fifth Fleet overseeing the Mideast, said authorities there were "aware of reports of this incident", but declined to comment further.
The reported attack comes after the US has alleged that in past months Iran attacked oil tankers near the Strait of Hormuz, at the mouth of the Persian Gulf, something denied by Tehran.
Friday's incident could push tensions between Iran and the US even higher, more than a year after US president Donald Trump unilaterally withdrew America from the nuclear deal and imposed sanctions now crushing Iran's economy.
The mysterious attacks on oil tankers near the Strait of Hormuz, Iran shooting down a US military surveillance drone and other incidents across the wider Middle East followed Mr Trump’s decision.
The latest assault saw Saudi Arabia’s vital oil industry come under a drone-and-cruise-missile attack, halving the kingdom’s output.
The US has blamed Iran for the attack, something denied by Tehran.
Yemen's Houthi rebels, whom the kingdom is fighting in a years-long war, claimed that assault, though analysts say the missiles used in the attack would not have the range to reach the sites from Yemen.