Amidst rising tensions in the Gulf following Iran’s seizure of the British-flagged Stena Impero, an audio recording supposedly between a British Royal Navy warship and an Iran Navy vessel has emerged. The recording is from moments before Stena Impero was seized, and is accompanied by a video of the moment masked forces dropped ropes down onto the ship from a helicopter.

“Steno Impero, Steno Impero, I say again, my last...You are ordered to change your course to 360 degrees immediately. If you obey, you will be safe,” says the voice purported to be that of an Iranian armed forces member in the recording. Following this, a British warship, Foxtrot 236, tells Stena Impero, "As you are conducting transit passage in a recognised international strait, under international law your passage must not be impaired, impeded, obstructed or hampered."

A voice supposedly from an Iran Navy vessel then tells the British warship, “Foxtrot 236 this is a separ navy patrol boat, no challenge is intended. No challenge is intended. I want and expect the ship for security reason, over.”

The separ navy patrol boat then tells Stena Impero to change its course by 360 degrees once again. “If you obey, you will be safe,” the voice says.

The radio recording was obtained by the British maritime security firm Dryad Global. The HMS Montrose, another British Royal Navy ship identifies itself and asks the Iranian vessel to confirm it is not "intending to violate international law" by attempting to board the tanker.

On Friday, the Stena Impero was seized by the Iranian Revolutionary Guard in a key shipping route in the Gulf. Twenty three crew members of Indian, Russian, Latvian, and Filipino origin are reported to be on board. Tehran has stated that the vessel is “violating international maritime rules.”

Video footage released by Iran's Revolutionary Guard-affiliated Fars news agency on Saturday appearing to show the moment the tanker was raided – masked persons are seen dropping down ropes on to the ship from a helicopter after it was surrounded by high-speed vessels.

The HMS Montrose was alerted and raced to intervene, however it was too far to stop the Stena Impero being seized as the tanker was already in Iranian waters.

Iran's IRNA news agency said the tanker was captured after it collided with a fishing boat and failed to respond to calls from the smaller craft. This was refuted by UK Foreign Secretary Jeremy Hunt who stated that the ship was seized in Omani waters, “in clear contravention of international law” and then forced to sail into Iran.

The Stena Impero's Swedish owner, Stena Bulk, said it had been fully complying with regulations and had been in international waters at the time. A second British-owned Liberian-flagged tanker, the MV Mesdar, was also boarded by armed guards on the same day but was released.

This comes after Royal Marines helped seize Iranian tanker Grace 1 off Gibraltar earlier this month, because of evidence it was carrying oil to Syria in breach of EU sanctions. Iran described the incident as "piracy" but UK Foreign Secretary Jeremy Hunt said the Grace 1 was detained legally in Gibraltarian waters "totally within the law".

(With IANS inputs)