The Athenian authorities have released the Iranian oil tanker detained by Greek court order, the Iranian Ports and Maritime Organization (PMO) said Tuesday in a statement.

The Greek court ordered the return of the detained oil tanker and its cargo to the owner, and Athens carried out the order, the PMO added.

This happened despite the legal assistance treaty between the United States and Greece and in light of mounting pressure from Washington on Athens to keep the ship and its cargo detained, it added.

The Greek government detained the ship earlier this year at the request of the US to enforce sanctions against Iran's oil. The US wanted to confiscate the Iranian oil carried by the tanker.

The Iranian port authority had announced in late May that the Greek authorities impounded a ship carrying the Iranian flag and confiscated its cargo by court order in coordination with the US government.

The port authority added that the ship sought shelter in Greek ports to protect the safety of its crew but received no aid, noting that the ship was unloaded by the army, in a step that is considered a clear example of piracy.

Originally, the ship was Russian-flagged - named Pegas - but it changed its flag to an Iranian one to avoid EU and US sanctions over the Ukraine war.

Iran's state news agency IRNA confirmed that the Iranian Foreign Ministry summoned the chargé d'affaires of Greece's embassy in Tehran in regard to the matter and informed him of the Iranian government's "strong objections".

Iranian media had reported that Iran's Coast Guard seized just days later two Greek oil tankers in the Gulf, the Delta Poseidon, and the Prudent Warrior, off the coast of Aslaviyeh and Bandar Lengeh, citing "violations", which Greece condemned as "tantamount to acts of piracy."