An Iranian tanker released after being detained for six weeks by the British overseas territory of Gibraltar is now headed for Lebanon, Turkey's Foreign Minister Mevlut Cavusoglu said on Friday.

"This tanker is not heading actually to Eskerun (in Turkey), this tanker is heading to Lebanon," Cavusoglu said during a visit to Oslo, referring to the Adrian Darya 1 vessel.

The ship was suspected of transporting crude oil to Syria, in violation of European sanctions against the country, and the US has called for it to be seized.

The minister did not specify whether Lebanon was the tanker's final destination.

"We still buy gas from Iran, but we don't buy oil," he stressed, adding that Turkey was monitoring the vessel's progress "very closely".

A court in the British territory ordered the tanker's release on August 15 despite a last-minute legal bid by the United States to have it detained.

The Adrian Darya 1 set sail three days later for the eastern Mediterranean, carrying 2.1 million barrels of oil worth more than $140 million.

Iran said on Monday it had sold the oil, but did not name the buyer.