An Iranian ship held by Gibraltar since July on suspicion of transporting oil to Syria has left port.
Marine tracking shows the tanker moving east into the Mediterranean and lists Kalamata in Greece as the destination.
Gibraltar earlier rejected a request by the US to again seize the ship, which has changed its name from Grace 1 to Adrian Darya-1.
Iran said it was ready to dispatch a naval escort to the Adrian Darya-1.
The ship with its crew of 29 – from India, Russia, Latvia and the Philippines – was seized with the help of British Marines on 4 July, after the government of Gibraltar – a British territory – suggested it was heading for Syria in breach of EU sanctions.
British-flagged tanker seized in July remains in Iranian hands. There had been speculation of a swap if Grace 1 was freed, despite official denials.