The Iranian oil tanker at the centre of a diplomatic dispute departed from Gibraltar late on Sunday after the British overseas territory rejected a US demand to seize the vessel.
Marine tracking shows the tanker moving east into the Mediterranean and lists Kalamata in Greece as the destination.
The ship, now renamed Adrian Darya 1, was previously known as Grace 1. It has a cargo of at least $130m worth of light crude oil.
Gibraltar’s Supreme Court ordered the release of the vessel after more than 40 days in detention,after receiving written assurances from Iran that the ship would not be headed for countries “subject to European Union sanctions”.
The US made the last-minute request on Friday, a day after Gibraltar lifted its detention order.
Gibraltar said it could not comply with Washington’s request to issue a new detention order because US sanctions against Iran did not apply in the EU.