The British-flagged oil tanker Stena Impero seized by Iran a couple of months ago has been released, the Ports and Maritime Organisation in the southern Iranian province of Hormozgan said.

"After the issuing of the ruling for the end of detention of the English tanker Stena Impero this vessel will soon, and after the passing of 65 days, begin its movement from the port of Bandar Abbas toward international waters," the head of the Ports and Maritime Organization of Iran in Hormozgan Province, Allahmorad Afifipour, said on Sunday, according to the semi-official news agency Tasnim.

Legal procedures were being carried out to allow the vessel out of Iranian waters, Afifipour continued, adding that there is an ongoing investigation into the alleged violation by the oil tanker, Efe news reported.

The British vessel, with 23 crew members on board, was seized on July 19 by the Islamic Revolutionary Guards in the Strait of Hormuz while on its way from the United Arab Emirates to Saudi Arabia.

Iranian authorities accused Stena Impero of violating maritime navigation rules, which London and the vessel's crew have denied.

The seizure came a couple of weeks after the confiscation of an Iranian oil tanker, Grace 1, by the British navy off the coast of Gibraltar due to suspicions that it carried oil to Syria, which would violate sanctions imposed by the European Union.

Iranian authorities had warned it would take action against the UK in retaliation for the seizure of Grace 1, which Tehran considered an act of piracy.

Grace 1, now known as Adrian Darya 1, was released in mid-August.