Iranian forces seized two Greek tankers in the Gulf on Friday, Iranian state media reported, shortly after Tehran warned it would take "punitive action" against Athens over the confiscation of Iranian oil by the United States from a tanker held off the Greek coast.
"The Revolutionary Guards Navy today seized two Greek tankers for violations in Gulf waters," said a Guards statement, quoted by the state news agency IRNA.
It gave no further details or say what the alleged violations were.
Greek authorities last month impounded the Iranian-flagged Pegas, with 19 Russian crew members on board, near the coast of the southern island of Evia due to EU sanctions.
The United States later confiscated the Iranian oil cargo held onboard and plans to send it to the United States on another vessel, Reuters reported on Thursday.
The Pegas was later released because of confusion about the sanctions over its owners.
Earlier on Friday, Nour News, which is affiliated to an Iranian state security body, said on Twitter: "Following the seizure of an Iranian tanker by the Greek government and the transfer of its oil to the Americans, #Iran has decided to take punitive action against #Greece."
It did not say what kind of action Iran would take.
The Pegas was among five vessels designated by Washington on Feb. 22 - two days before Russia's invasion of Ukraine - for sanctions against Promsvyazbank, a bank viewed as critical to Russia's defense sector.
It was unclear whether the cargo was impounded because it was Iranian oil or due to the sanctions on the tanker over its Russian links. Iran and Russia face separate US sanctions.
Also on Friday, Iran summoned an envoy of Switzerland, which represents US interests in Tehran, to protest against the Pegas oil seizure, the Iranian foreign ministry said.
"The Islamic Republic expressed its deep concern over the US government's continued violation of international laws and international maritime conventions," state media quoted the foreign ministry as saying.
A spokesperson for the US Department of Justice declined to comment on the oil seizure.
IRNA quoted Iran's Ports and Maritime Organization as saying the tanker had sought refuge along the Greek coast after experiencing technical problems and poor weather. It called the seizure of its cargo was "a clear example of piracy."
The United States on Wednesday imposed sanctions on what it described as a Russian-backed oil smuggling and money laundering network for Iran's Revolutionary Guards' Quds Force.
In 2019, Iran seized a British tanker near the Strait of Hormuz for alleged marine violations two weeks after British forces detained an Iranian tanker near Gibraltar, accusing it of shipping oil to Syria in violation of European Union sanctions. Both vessels were later released.