An oil tanker caught up in a dispute last year between the United States and Iran was boarded by armed individuals off the coast of Oman on January 11 and appeared to have changed course towards Iran, Reuters reported, citing UK maritime sources.

The Marshall Islands-flagged tanker St Nikolas was boarded by armed intruders as it sailed close to the Omani city of Sohar, according to British maritime security firm Ambrey, and its AIS tracking system was turned off as it headed in the direction of the Iranian port of Bandar-e-Jask.

In 2023 the St Nikolas was seized by the United States in a sanctions enforcement operation when it sailed under a different name, Suez Rajan.

The United States said at the time that Iran's Islamic Revolution Guards Corps (IRGC) had been trying to send contraband Iranian oil to China, in violation of US sanctions.

The ship had loaded 145,000 tonnes of oil in the Iraqi port of Basra and was heading to Aliaga in western Turkey via the Suez Canal, its operator Empire Navigation told Reuters, adding that it had lost contact with the vessel.

Thursday's incident is located close to the Strait of Hormuz, between Oman and Iran.

The vessel is manned by a crew of 19 including 18 Filipino nationals and one Greek national, the operator said, adding it was chartered by Turkish oil refiner Tupras (TUPRS.IS).

The United Kingdom Maritime Trade Operations (UKMTO) authority said earlier on Thursday, January 11, it had received a report that a vessel located around 50 nautical miles (93 km)  east of Oman's coast was boarded by four to five armed persons.

The armed intruders were reported to be wearing military-style black uniforms and black masks.

UKMTO said the chief security officer reported the vessel had altered course towards Iranian territorial waters and that communication with the tanker had been lost.

The UK authority, which provides maritime security information, said it was unable to make further contact with the vessel and authorities were still investigating the incident.

The Suez Rajan was carrying more than 980,000 barrels of Iranian crude oil last year when it was seized and the oil confiscated.

It was unable to unload the Iranian crude for nearly two and half months over fears of secondary sanctions on vessels used to unload it. It was renamed the St Nikolas after unloading the cargoes.