Iran’s foreign ministry has reportedly summoned the envoy of Switzerland, which represents Washington’s interests in Tehran, to protest against the American seizure of Iranian oil from a Russian-operated ship in Greek waters.

The ministry also called for the immediate release of the ship and its cargo, the IRNA state news agency reported on Friday.

“The Islamic Republic expressed its deep concern over the US government’s continued violation of international laws and international maritime conventions,” IRNA and other media outlets quoted the foreign ministry as saying.

The Swiss envoy told Iranian officials he would convey Tehran’s message to Washington, IRNA reported. The developments came after the cargo ship was seized on Wednesday.

The news agency quoted Iran’s Ports and Maritime Organization as saying the tanker – named the Pegas – had sought refuge along the Greek coast after experiencing technical problems and poor weather, adding the confiscation of its cargo was “a clear example of piracy”.

Separately on Wednesday, the US imposed sanctions on what it described as a Russian-backed oil smuggling and money laundering network for Iran’s Islamic Revolutionary Guard Corps (IRGC).

US sanctions

The Iranian-flagged Pegas was among five vessels designated by Washington on February 22 – two days before Russia’s invasion of Ukraine – for sanctions against Promsvyazbank, a bank viewed as critical to Russia’s defence sector.

The vessel’s Russian owner Transmorflot was subsequently designated on May 8. The tanker, renamed Lana on March 1 and flying the Iranian flag since May 1, has remained near Greek waters since then. It was previously Russian flagged.

It was unclear whether the ship’s cargo was impounded because it was Iranian oil or because of the sanctions on the tanker over its Russian nexus. Iran and Russia face separate US sanctions.

A spokesperson for the US Department of Justice declined to comment on the oil seizure but three sources familiar with the matter told the Reuters news agency on Thursday that Washington plans to send the cargo on board the Pegas to the US on another vessel.

The row over the tanker has taken place against the backdrop of tense efforts to revive the 2015 nuclear deal between Iran, the US and several other world powers.

On Wednesday, US President Joe Biden’s special envoy for Iran acknowledged that prospects of restoring the agreement are “tenuous at best” amid as of yet unmet demands from Tehran for Washington to remove the IRGC from its list of “foreign terrorist organisations”.

The 2015 deal saw sanctions lifted on Iran in return for curbs on the country’s nuclear programme. Former US President Donald Trump unilaterally withdrew from the accord in 2018.