An oil tanker was boarded by "armed unauthorised persons" in military uniforms and masks on Thursday morning off the coast of Oman.

Report informs via foreign media that the situation remains unclear but suspicion immediately fell on Iran, as the vessel was once involved in a dispute with the US Justice Department that saw a million barrels of Iranian crude oil seized.

The United Kingdom Maritime Trade Operations (UKTMO), which provides warnings to sailors in the Middle East, said the incident began early in the morning 50 miles off the coast of Oman.

UKTMO described receiving a report from the ship's security manager of hearing "unknown voices over the phone" alongside the ship's captain.

It said it was unable to make further contact with the vessel and that the authorities were investigating the incident.

The development comes amid high tensions in the nearby Red Sea, where attacks by Houthi rebels based in Yemen are disrupting shipping.