President Moon Jae-in has ordered his officials to explore filing a complaint to the International Tribunal for the Law of the Sea against Japan's decision to release contaminated water from its Fukushima nuclear plant.
The South Korean leader also expressed his concerns as Tokyo's new ambassador to Seoul presented his credentials on Wednesday.
"President Moon told Ambassador Koichi Aiboshi that there are much concerns in South Korea about Japan's decision as a country that is geographically the closest and shares the sea with Japan.
He asked the envoy to convey his message to Tokyo."
On Tuesday, Japan unveiled plans to release more than one million tons of contaminated water into the sea from the plant crippled by a 2011 earthquake and tsunami starting in about two years after filtering it to remove harmful isotopes.
A series of nationwide protests against the move by politicians, local officials, fishermen and environmental activists took place in South Korea on Wednesday.
It also prompted South Korea's nuclear watchdog to send a letter to Japan's Nuclear Regulation Authority, whose approval is mandatory for the discharge to be executed.
"We have requested Japan's Nuclear Regulation Authority to conduct an objective and independent evaluation of Tokyo Electric Corporation's discharge plan on whether it meets international standards. We've also asked them to closely monitor the implementation and share their conclusion in a swift and transparent manner."
South Korea also plans to work together with neighboring countries and related international organizations for a scientific and objective review of Japan's discharge plan.
Kim Min-ji, Arirang News.