The Iranian government on Tuesday denied that it is holding a South Korean-flagged tanker and its crew hostage, retorting that South Korea is the “hostage” taker for freezing $7 billion in Iranian funds after the United States re-imposed sanctions against Tehran.

The tanker Hankuk Chemi was seized in the Persian Gulf on Monday by a swarm of speedboats operated by Iran’s Islamic Revolutionary Guard Corps (IRGC), a designated terrorist organization. The ship and its crew of 20 were taken to the IRGC port facility in Bandar Abbas and detained, ostensibly because the ship was “polluting” the Persian Gulf. The company that operates the tanker, DM Shipping Co. Ltd., dismissed those allegations as “absurd.”

The South Korean government protested the seizure of the ship, underlining its protest by dispatching an anti-piracy squad called the Cheonghae Unit to the Persian Gulf. South Korean officials told CNN on Tuesday that the Cheonghae Unit, which includes special forces operators, is not planning a raid to rescue the sailors, but will instead advise other South Korean-flagged vessels on safety procedures.

On Tuesday, Iran responded by essentially taunting the South Koreans and implying the crisis is fair retaliation for Seoul freezing Iranian assets.

“We’ve become used to such allegations,” Iranian spokesman Ali Rabei replied when asked by reporters if the capture of the Hankuk Chemi was an act of piracy. “But if there is any hostage-taking, it is Korea’s government that is holding $7 billion – which belongs to us – hostage on baseless grounds.”

The New York Times noted on Tuesday that Iranian media outlets linked to the IRGC are triumphantly describing the captive sailors as “revenue thieves” who were “captured” by Iranian forces.

South Korean diplomats met with Iranian Ambassador Saeed Badamachi Shabestari on Tuesday to protest the capture of the Hankuk Chemi and demand the swift release of the ship and crew.

South Korean Foreign Minister Kang Kyung-wha said on Tuesday that every diplomatic effort was being made to ensure the safety of the prisoners, and a delegation is on its way to Iran to negotiate their release. Five of the prisoners are South Korean nationals, while the others are from Myanmar, Indonesia, and Vietnam.

“The seizure came amid tensions between Seoul and Tehran over Iranian financial assets frozen under U.S. sanctions. News reports said that Tehran was considering proposing to Seoul that the two countries barter the frozen money for COVID-19 vaccines and other goods,” South Korea’s Yonhap News reported.