South Korean President Moon Jae-in delivered a message of "great concern" Wednesday over Japan's decision to dump a huge amount of contaminated wastewater from a crippled nuclear plant into the Pacific Ocean.

Speaking directly to Japan's new ambassador here, Koichi Aiboshi, the president said that there is great concern among South Koreans, as the two nations are geographically close to each other and share the sea, according to Cheong Wa Dae spokesman Kang Min-seok.

He asked the envoy to convey his message to Tokyo during a conversation following a ceremony to receive his credentials at Cheong Wa Dae.

The previous day, the Japanese government announced a plan to release what it calls "treated water" from Fukushima Daiichi Nuclear Power Plant into the waters.

In an internal meeting earlier Wednesday, Moon instructed his government to "proactively consider" bringing the matter to the International Tribunal for the Law of the Sea, Kang added. (Yonhap)