UK Maritime Trade Operations, part of the Department of Defense, described the incident about 60 miles (97 km) east of Fujairah as a “potential diversion”.
A group of eight or nine armed individuals are said to have boarded the ship, named Asphalt Princess, the security source told Sky News.
“It was an unauthorized embarkation in the Gulf of Oman,” said the security source.
There is no UK connection to the tanker, but a spokesperson for the UK Foreign Office said: “We are urgently investigating an incident on a ship off the coast of the United Arab Emirates.”
It comes as The Associated Press reported that at least four ships have sent out warnings saying they have lost control of their direction.
Iran’s foreign ministry said reports of the incident were “suspect”, but warned against any attempt to create a “false atmosphere” against Tehran.
The tankers – Queen Ematha, Golden Brilliant, Jag Pooja and Abyss – all reported through their automatic identification system trackers that they were “not under command,” according to MarineTraffic.com.
Usually this means that a ship has lost power and can no longer steer.
He follows a suspicious drone attack on the Mercer Street ship, which was blamed on Iran by the US, UK and Israel.
British special forces are participating in the investigation into what happened aboard the Israel-linked ship last week.
Mercer Street is owned by Japanese people, but sailed with a Liberian flag.
Zodiac Maritime, the British company that manages the ship, is part of the Zodiac group of Israeli billionaire Eyal Ofer.
The incident resulted in the deaths of a British security guard on board the ship and a Romanian crew member.
Iran’s ambassador to the UK was summoned yesterday by the Foreign, Commonwealth and Development Department following the Mercer Street incident.
Prime Minister Boris Johnson said Iran had to “face the consequences” of its actions, adding that the Mercer Street incident “was clearly an unacceptable and outrageous attack on commercial shipping, a British national has died”.
Foreign Minister Dominic Raab has pledged to work with the allies on a “concerted response”.