Oil prices rose early on Thursday on reports that two tankers have been attacked in the Gulf of Oman, with crews being evacuated.
Upstream's sister shipping publication TradeWinds reported that the vessels, one of which is in the fleet of Seadrill boss John Fredriksen's tanker-owning company Frontline, were the subject of torpedo attacks on Thursday.
The British Navy's UK Maritime Trade Operations said on its website it is "aware of an incident" in the region and it and its partners "are currently investigating".
The US Fifth Fleet, operating out of Bahrain, said: "We are aware of the reported attack on shipping vessels in the Gulf of Oman.
"US Naval Forces in the region received two separate distress calls at 6:12am local (Bahrain) time and a second one at 7:00am.
"US Navy ships are in the area and are rendering assistance."
Brent spot prices rose more than 3% early on Thursday on the back of the reported attacks, edging over $61.60 per barrel before 8:30am London time.
By about midday they were up almost 4% to just over $62.
TradeWinds reported the tankers as the 110,000-dwt, Marshall Islands-flagged Front Altair and the 27,000-dwt, Panama-flagged Kokuka Courageous.
It said that all crew have abandoned the Frontline-managed Front Altair and been picked up by a passing vessel.
The Kokuka Courageous, managed by Bernhard Schulte, has "fallen silent" and is not contactable, TradeWinds said, citing sources.
Reports indicate the Front Altair was en route to Japan with a cargo of naphtha, while the Kokuka Courageous was en route from Saudi Arabia to Singapore with a cargo of methanol.
A statement issued on behalf of International Tanker Management (ITM), which is the ISM manager of the Front Altair, said that a fire broke out on board the vessel.
"The master took the prudent measure of abandoning the vessel and the 23 crew members, who were safe and unharmed, were picked up by the Hyundai Dubai" - which is a 30,100-dwt, Marshall Islands-flagged general cargo vessel.
"The Front Altair was at the southern end of the Strait of Hormuz in international waters when the incident occurred and is carrying a cargo on naphtha."
The statement continued: "Managers are working on plans to salvage the vessel. An investigation is under way as to the cause of the explosion which is as yet unknown."
Bernhard Schulte Shipmanagement (BSM), manager of the Kokuka Courageous, said one crew member was slightly injured in the incident, which led to all 21 abandoning ship and being picked up from a lifeboat by the passing vessel Coastal Ace.
"The Kokuka Courageous remains in the area and is not in any danger of sinking. The cargo of methanol is intact," the statement read.
"BSM’s top priority is the wellbeing of the 21 crew on board our managed vessel. The Coastal Ace is in the vicinity at a safe distance from the Kokuka Courageous.
"The vessel is about 70 nautical miles from Fujairah and about 14 nautical miles from the coast of Iran.
"The Coastal Ace is now awaiting instructions from the (UKMTO) which is responding to the incident."
The attacks come only a matter of weeks after four tankers were assaulted in the area, just off the United Arab Emirates port of Fujairah.
Two of those tankers were in the fleet of Saudi state player Bahri, with Saudi and other authorities pointing the finger of blame at Iran or forces linked to the Tehran administration. The Iranian government has denied any involvement in those assaults.
Two days after those attacks, two Saudi Aramco oil pumping stations in Saudi Arabia allegedly came under drone attack.