Armed troops from Iran's Revolutionary Guard Corps stormed a South Korean tanker and forced the ship to travel to Iran, the vessel's owner said on Tuesday.
Iran had said the vessel was polluting the Persian Gulf and Strait of Hormuz but the latest maritime seizure came ahead of negotiations over Iranian assets frozen in South Korean banks and amid increased tensions with the West over its nuclear program.
Iran on Monday said it was enriching uranium up to 20%, a small technical step away from weapons-grade levels of 90%, at its underground Fordo facility.
That move appeared aimed at pressuring the US in the final days of President Donald Trump's administration, which unilaterally withdrew from the Iran nuclear deal.
It also comes ahead of the inauguration of President-elect Joe Biden who said he would re-join the international deal.
The South Korean vessel had been travelling from Saudi Arabia to the UAE when Iranian forces boarded the ship, the AP reported, after speaking to an official at the shipping company.
The official, who spoke anonymously as he was not authorised to speak with journalists, said Iranian troops stormed the tanker and demanded the captain sail into Iranian waters.
The company has since been unable to reach the captain, the official told the AP. Security cameras installed on the ship that initially relayed footage on the scene on the deck to the company are now turned off, the official said.
In past months Iran has sought to escalate pressure on South Korea to unlock billions of dollars in frozen assets from oil sales earned before the Trump administration tightened sanctions on the country’s oil exports.
The head of Iran’s central bank recently announced that the country was seeking to use funds tied up in a South Korean bank to purchase coronavirus vaccines through COVAX, an international program designed to distribute COVID-19 vaccines to participating countries.
South Korea’s Foreign Ministry demanded the ship’s release, saying in a statement that its crew was safe. The defence ministry said it would send an anti-piracy unit to near the Strait of Hormuz — a 4,400-ton-class destroyer with about 300 troops.
The US State Department called for the tanker’s immediate release, accusing Iran of threatening “navigational rights and freedoms” in the Persian Gulf in order to “extort the international community into relieving the pressure of sanctions.”
Last year, Iran similarly seized a British-flagged oil tanker and held it for months after one of its tankers was held off Gibraltar.
The latest incidents coincide with the anniversary of the US drone strike that killed Guard Gen. Qassem Soleimani in Baghdad last January.
As the anniversary approached and fears grew of possible Iranian retaliation, the US dispatched B-52 bombers over the region and ordered a nuclear-powered submarine into the Persian Gulf.