Iran's Revolutionary Guards fired at least two missiles at commercial ships transiting through the Strait of Hormuz on Monday night.
Two commercial ships suffered significant damage but had no casualties, Axios reported, citing a US official.
Separately, Britain's maritime security agency said a tanker caught fire after being hit by an unknown projectile east of Oman's Limah early on Tuesday.
The United Kingdom Maritime Trade Operations agency (UKMTO) said early on Tuesday that the tanker was struck on its port side while travelling southbound about 15 km east of Limah, causing a fire. No casualties or environmental impact had been reported.
US Central Command did not immediately respond to a request for comment.
Oil gained following the attacks, highlighting continued risks to traffic in the waterway. Brent rose toward $73 a barrel, while West Texas Intermediate was above $69. Prices fell by 30 per cent when the US and Iran struck a tentative ceasefire deal last month.
The reports underscored the risks to shipping around the Strait of Hormuz, the narrow waterway between Iran and Oman through which about a fifth of global oil consumption passes.
Commercial vessels have come under attack during the war that began with US-Israeli strikes on Iran, despite an interim agreement that included safe-passage provisions.
Indirect US-Iran talks ended last week without any public sign of headway toward a lasting peace, despite a 60-day ceasefire intended to create space for diplomacy following the US and Israeli strikes that triggered the conflict.
President Donald Trump said on Monday the US would either reach a deal with Iran or "finish the job," renewing his threat of military action as Tehran projects defiance following the funeral of former Supreme Leader Ayatollah Ali Khamenei.
'READY TO FIRE AT YOU'
Iran's Revolutionary Guards warned ships via maritime radio over the weekend that "our missiles and drones are ready to fire at you," the Wall Street Journal reported, quoting from a recording it obtained.
One of the vessels under attack appeared to be Al Rekayyat, a liquefied natural gas tanker owned and managed by Nakilat, also known as Qatar Gas Transport Company, which operates one of the world's largest LNG shipping fleets. The ship was hit on the port side, at the top of the engine room, the WSJ report said.
"Engine room fire and full of smoke. Unable to assess further damage. All crew are safe and mustered on the starboard side," the recording said.
The vessel was at the mouth of the strait, in the Gulf of Oman, when it was attacked.
Nakilat, QatarEnergy and Qatar's International Media Office did not immediately respond to requests for comment.
Investors have been keeping a close eye on talks between the U.S. and Iran over the fate of shipping through the
- Reuters and inputs from media reports
