Two Greek tankers The oil tanker, bound for Houston in the United States, was seized on Thursday in the Gulf Bay, Iran's Revolutionary Guard Navy announced today. The seizure follows the seizure of an Iranian oil tanker off the coast of Greece.

"The Revolutionary Guard Navy seized two Greek cargo ships today [Friday] for violations in Gulf waters," the Guard said in a statement.

The announcement came after Iran announced that it would respond to Greece over the seizure of Iranian oil off its coast. Iran has also summoned a Swiss envoy representing US interests in Tehran.

The Iranian call is intended as a protest against the seizure of Iranian oil by the US from a Russian-operated ship near Greece, Iran's Foreign Ministry announced. For its part, Greece has accused Iran of piracy, and has recommended that Greek citizens avoid traveling to the country, the Greek Ministry of Foreign Affairs (MFA) said in a statement.

Athens said that the Iranian navy landed armed troops on the two cargo ships via helicopter. One of the ships, the Delta Poseidon, was in international waters, according to a statement from the Greek MFA. The second ship, the Prudent Warrior, is operated by the Greek company Polembros, which said it was unable to communicate with the ship at the moment. According to the Greek MFA, the Prudent Warrior was near the Iranian coast when it was seized.

In response, the US Navy has already said it is investigating the Iranian seizure, and Athens has also informed the European Union and the International Maritime Organization of the incident.