TEHRAN, Iran — Iran’s Foreign Ministry summoned the chief of Greece’s diplomatic mission for allegedly seizing cargo from a vessel flying the Iranian flag in Greek waters, state media reported Wednesday.

The IRNA news agency reported that an Iran-flagged ship had to stop in Greek waters due to technical problems and was being held by the Greek government off of Greece’s coast. The news agency claimed the vessel’s cargo was confiscated with a court order under pressure from the United States. The report didn’t say what the cargo was.

Iran’s Foreign Ministry called the measure “international piracy.”

There was no immediate comment from Greek officials.

The semi-official Mehr news agency reported that Iran’s ports and maritime organization said the vessel was a tanker operating under the Iranian flag and that it had faced bad weather conditions and experienced some technical problems. That led the vessel’s crew to call for assistance, according to the report.

The incident comes amid heightened tensions between the U.S. and Iran, which has been under international sanctions since former President Donald Trump withdrew the U.S. from Iran’s 2015 nuclear accord with world powers in 2018.

The U.S. seized the cargo of two tankers suspected of transporting Iranian oil as part of an elaborate sanctions-busting scheme involving forged documents and the repainting of a ship’s deck to cloak illegal shipments.

Details of the seizure were contained in a federal civil case unsealed in February after the Greek-managed vessels discharged their valuable cargo, worth about $38 million, in Houston and the Bahamas at the direction of U.S. law enforcement.