Iran's paramilitary Revolutionary Guard has seized two Greek oil tankers in the Persian Gulf, just after Greece assisted the US in seizing an Iranian oil tanker over alleged sanctions violations in the Mediterranean Sea.
The Guard's announcement comes as tensions remain high between Iran and world powers over stalled negotiations regarding its nuclear program.
The Guard issued a statement on its website, accusing the unnamed tankers of unspecified violations.
Greece's foreign ministry said it made a strong demarche to the Iranian ambassador in Athens over the "violent taking over of two Greek-flagged ships" in the Persian Gulf.
"These acts effectively amount to acts of piracy," a ministry statement said.
The ministry called for the immediate release of the vessels and their crews, and said these acts would have "particularly negative consequences" in bilateral relations and in Iran's relations with the European Union, of which Greece is a member.
The ministry's statement said that earlier on Friday, an Iranian helicopter landed on the Greek-flagged Delta Poseidon in international waters 22 nautical miles off the coast of Iran.
"Armed men then took the crew captive," it said, adding that two Greek citizens were among the crew.
"A similar incident has been reported on another Greek-flagged vessel, that was carrying seven Greek citizens, close to the coast of Iran," the ministry said.
A US defence official, speaking on condition of anonymity to discuss intelligence matters, said it appeared the two ships had come close to - but not in - Iranian territorial waters on Friday before drifting off into Iranian waters.
The ships also had turned off their tracking devices, another red flag, the official said.
However, neither had issued a mayday or a call for help, the official said.
Iran had threatened to take "punitive action" earlier on Friday over Greece being involved in the US seizure of an Iranian oil tanker in Greek waters.
Iran's Nour News website, close to its security services, carried the threat just as shipping news site Lloyd's List said it believed two Greek tankers had been seized in the Persian Gulf.
Quoting anonymous industry sources, Lloyd's reported that the two ships had been boarded after Iranian military helicopters approached them on Friday afternoon.
It said both tankers had just been loaded with Iraqi crude oil.
The crude oil cargo of an Iranian-flagged tanker that was stopped in Greek waters last month has been seized and is being transferred to another vessel following a request from the US, a Greek official said on Thursday.
The official said following a "judicial intervention by US authorities concerning the ship's cargo" the process is currently underway, at US government expense, for the oil "to be handed over" off the port of Karystos on the Aegean Sea island of Evia.
The official, who asked not to be identified in order to discuss the case, did not provide further details.
Australian Associated Press
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