Iranian forces are believed to have seized a Marshall Islands-flagged tanker managed by Cyprus-based Columbia Shipmanagement after it abruptly changed course in the Gulf of Oman while sailing from the United Arab Emirates to Singapore.

According to British maritime security firm Ambrey, the Talara oil tanker, owned by Cyprus-registered Pasha Finance Inc. and located 22 nautical miles east of Khor Fakkan, was approached by three small boats while transiting the Strait of Hormuz before veering off its route.

UK Maritime Trade Operations described the incident as a “suspicious event”, confirming the vessel later headed towards Iranian territorial waters.

Two independent shipping sources told Reuters their initial assessment was that units of Iran’s Revolutionary Guard Corps had directed the tanker towards the coast.

Columbia Shipmanagement said it had lost all contact with the vessel, which was carrying high-sulphur gasoil from Sharjah to Singapore.

The company “notified the relevant authorities and is working closely with all relevant parties, including maritime security agencies and the vessel owner, to restore contact with the vessel,” the firm said, adding that “the safety of the crew remains our foremost priority.”

The incident comes amid heightened tension in the Strait of Hormuz, where Iran has stepped up inspections and previous ship seizures. In late October, the Iranian judiciary said it had opened a prosecution linked to last year’s seizure of the container ship MSC Aries