WASHINGTON -- The US State Department on Monday called on Iran to immediately release a South Korea-flagged tanker it detained.

The State Department argued Iran's detention of the South Korean tanker may be part of an attempt to force the international community to remove its sanctions on the country.

"The United States is tracking reports that the Iranian regime has detained a Republic of Korea-flagged tanker," a department spokesperson told Yonhap News Agency, referring to South Korea by its official name.

"The regime continues to threaten navigational rights and freedoms in the Persian Gulf as part of a clear attempt to extort the international community into relieving the pressure of sanctions. We join the Republic of Korea's call for Iran to immediately release the tanker," the spokesperson added, while asking not to be identified.

The remarks came hours after the Seoul government said the tanker, MT Hankuk Chemi, has been seized by Iran's Islamic Revolution Guards Corps for allegedly polluting waters off Iran.

Iran has since reportedly claimed the seizure was purely "technical" and that the issue would be dealt with by Iran's judicial officials.

The South Korean owner of the ship says the ship was sailing in international waters when it was seized. (Yonhap)