Iran has summoned chargé d'affaires of Switzerland that represents Washington’s interests in Tehran to protest the US seizure of Iranian oil cargo from a Russian-operated ship in Greece's territorial waters.

Demanding the immediate release of the seized ship and its confiscated cargo, the Iranian foreign ministry’s department for American Affairs said in a statement on Friday, “The Swiss chargé d'affaires was summoned to convey Iran’s concern and strong protest over the continued violation of international laws and maritime conventions concerning free navigation and trade by the US administration.”

According to the statement, the Swiss envoy assured that he would convey Iran’s message to American officials.

On Wednesday, the Islamic Republic summoned the Greek chargé d'affaires to protest the seizure of the vessel carrying Iranian crude.

The Russia-flagged aframax Lana, formerly named Pegas, was detained on April 15 by Greek authorities and had been waiting at Karistos port pending a court ruling. On Monday afternoon, a tanker owned by Dynacom Tankers Management, called Ice Energy, was chartered by the US Department of Justice and started a ship-to-ship transfer of the US-sanctioned Iranian crude on the basis of Russian sanctions.

The operation, first reported by watchdog group United Against Iran, was verified using Lloyd's List intelligence data.

Lana, which arrived off Greece early in April with reports of a possible mechanical failure and anchored south of the Greek island of Evia, was identified as the Russian-flagged Pegas and the assumption at the time was that it was laden with Russian crude.