London (AFP) - Iranian forces ordered a British-flagged tanker in the Gulf to change course, telling the Stena Impero it would be safe "if you obey", according to a verified audio recording released Sunday.
The recording of radio communications between the Stena Impero, British warship HMS Montrose and the advancing Iranian forces was obtained and released by London-based maritime security risk analysts Dryad Global, and confirmed as genuine by Britain's Ministry of Defence (MoD).
Iranian forces seized the Swedish-owned tanker on Friday in what Britain says was an illegal operation in Omani waters.
Video footage released by Iran's Islamic Revolutionary Guard Corps on Saturday showed a ship with the tanker's markings being surrounded by speedboats before troops in balaclavas descended onto the vessel by rope from a helicopter.
In the audio recordings, the Iranians told the Stena Impero: "You are ordered: change your course to three six zero. Three six zero degrees immediately. If you obey, you will be safe."
The frigate HMS Montrose (F236), in the Gulf to provide maritime security to merchant shipping, told the 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."
Communication is established between HMS Montrose and the Iranians.
They told the British warship: "Foxtrot 236 this is SEPAH navy patrol boat. No challenge is intended. No challenge is intended. I want to inspect the ship for security reason."
HMS Montrose replied: "SEPAH navy patrol boat, this is British warship Foxtrot 236. Your requests that you are transmitting to the Stena Impero... hinder and impede her passage. You must not impair, impede, obstruct or hamper the passage of the MV Stena Impero.
"Please confirm that you are not intending to violate international law by unlawfully attempting to board the MV Stena."
The message from the Iranians to the Stena Impero was repeated: "If you obey, you will be safe."
The MoD confirmed that the recording was genuine.
"We've just had that verified. That is legitimate," the ministry told AFP.
Iran detained the Stena Impero on allegations it failed to respond to distress calls and turned off its transponder after hitting a fishing boat.
HMS Montrose earlier this month intercepted Iranian patrol boats surrounding another UK-flagged tanker.