BBC Reports The MT Hankuk Chemi was seized by Iranian forces near the strategic Strait of Hormuz, and its crew of 20 detained. Iran said the ship had violated environmental rules.
The incident comes amid tensions over Iranian funds frozen in South Korean banks because of US sanctions.
A senior South Korean official was due in Iran in the coming days to discuss the issue.
But an official told Reuters news agency that “the plan is unclear” as to whether Vice Foreign Minister Choi Jong-kun’s visit would still go ahead.
Meanwhile, Foreign Minister Kang Kyung-wha told reporters that South Korea was making diplomatic efforts to try to secure the release of the tanker and its crew, which includes sailors from Indonesia, Myanmar, South Korea and Vietnam.
“We have been trying to figure out what happened through the Iranian Embassy in South Korea and the South Korean Embassy in Iran and continuing to make efforts to address this situation,” she said, according to Yonhap news agency.
South Korea’s Defence Ministry on Tuesday said it had dispatched its anti-piracy unit to waters near the Strait of Hormuz, a narrow shipping route in the Gulf region, to “ensure the safety” of South Korean nationals.
In a statement, Iran’s foreign ministry spokesman said the chemical tanker’s seizure was over a “purely technical issue and due to polluting the sea”.
The ship’s operator has denied that the vessel was polluting waters.
The incident marks the first Iranian seizure of a major vessel in more than a year.