File photo: AFP

The Iranian oil tanker seized by Britain for weeks has left Gibraltar for internationals waters, Iran's Ambassador to Britain Hamid Baeidinejad confirmed Monday on his social media accounts.

According to the monitoring website Marine Traffic, the supertanker -- which had been detained since July 4 off the coast of Gibraltar -- lifted anchor Sunday evening and started sailing south.

Gibraltar seized the Grace 1 on July 4 on suspicion it was transporting oil to Syria in breach of European Union sanctions. Iran has repeatedly denied any violations.

A Gibraltar judge ordered the tanker released last Thursday, with Iranian officials saying a new crew had arrived to pilot the vessel -- now renamed the Adrian Darya -- and its 2.1 million barrels of oil.

But on Friday, the US Justice Department filed a last-minute request to detain the ship, alleging it was involved in supporting illicit shipments to Syria by Iran's Islamic Revolutionary Guard Corps, listed as a terrorist group by Washington.

Gibraltar's government rejected that request, saying it could not seek a court order to detain the supertanker because US sanctions against Iran were not applicable in the European Union.