The leader of the main opposition Democratic Party on Friday denounced Japan's release of contaminated water from the crippled Fukushima nuclear power plant as an act of crime against humanity, even labeling President Yoon Suk Yeol as an accomplice.

Rep. Lee Jae-myung made the remarks as Tokyo initiated the discharge of contaminated water a day earlier, a process expected to span more than three decades, despite lingering health and environmental concerns from neighboring countries.

"Japan has ultimately chosen the path of an environmental war criminal," Lee said during a party meeting, adding that the administration of Prime Minister Fumio Kishida would be recorded in history as the criminal that committed environmental terrorism against humanity.

The DP has strongly opposed the Fukushima release plan, arguing that it poses great health risks. However, the Yoon administration has stated that the release would pose no significant risk as long as it is done in a scientifically safe manner.

"I cannot believe the fact that the president has not said a single word regarding the water discharge issue," Lee said, calling on Yoon to end the silence and seek compensation from Tokyo.

Following the ocean discharge, Prime Minister Han Duck-soo said that "excessive worry" is unnecessary, as the ocean disposal plan, if executed accordingly, should not result in significant harm. He also criticized "fake news" and political instigation, saying they are threatening the fisheries industry without any scientific grounds.

"The source of fake news is actually the government that puts the livelihood of fishermen and the people's health at risk by silencing people and condoning the discharge of contaminated water," Lee said.

The DP has said it will step up the anti-discharge campaign, including holding street rallies. More protests are scheduled for over the weekend. (Yonhap)