Iran has sold the oil on board its Grace 1 tanker, renamed the Adrian Darya 1, which was released from UK custody in Gibraltar earlier this month.
The announcement was made by Iranian government spokesman Ali Rabiei, but the buyer, who will decide on the oil's next destination, was not identified.
Immediately after its release, the vessel headed for Kalamata, Greece, but was forced to change course when the Greek government said it would not endanger its relations with the United States by aiding an Iranian supertanker.
It was then reported that the Grace 1 would travel to the Turkish port of Mersin, but shipping data showed on Monday that the tanker was no longer bound there.
Tracking information showed that the tanker was just west of Crete as of Monday lunchtime.
The Grace 1 was released on August 18 after being held for five weeks on suspicion of carrying oil to Syria in breach of European Union sanctions.
The US federal court also ordered the seizure of the vessel, claiming that it has links to Iran's Islamic Revolutionary Guard Corps, which Washington has designated a terrorist organisation, soon after the detention order was lifted. The petition was rejected by Gibraltar.
Iran said any US move to seize the vessel again would have "heavy consequences".
Tension between Washington and Tehran has spiralled in recent months over US sanctions on Iranian oil exports.
Also on Monday, Iran announced that it has deployed destroyer Sahand to the Gulf of Aden, near Yemen, where the UAE and Saudi Arabia have been fighting the Iranian-backed Houthi rebels since 2015.
Rear Admiral Habibollah Sayyari, the chief of staff of the Iranian Army, told news agency IRNA on Monday that the warship is accompanied by a logistical vessel and the Kharg helicopter carrier on the voyage. It will escort Iranian ships in the Sea of Oman and the Arabian Gulf.
The Iran-aligned Press TV said that the destroyer is equipped with torpedo launchers, anti-ship and anti-aircraft guns, and missile systems.
The United Kingdom announced on Sunday that it has sent a third warship to the Arabian Gulf to defend freedom of navigation after a British-flagged tanker was seized by Iran in the Strait of Hormuz.
The IRGC seized the Stena Impero, a Swedish-owned tanker sailing under the British flag, detaining its crew of 23 on July 20.