South Korea’s main opposition party warned it would take a series of actions condemning the Yoon Suk Yeol administration’s policies on Japan as Tokyo began a phased release of treated wastewater from the Fukushima nuclear power plant on Thursday afternoon.

Rep. Lee Jae-myung, the head of the Democratic Party of Korea, said in an emergency meeting gathering all of the party’s lawmakers that Yoon, with his “leniency with Japan,” was “no less responsible for the destruction of our seas being undertaken by the Japanese government.”

“The Yoon administration practically acted as a spokesperson for Japan, even as it was going to pollute our waters with radioactive waste,” he said. “Our party will not stop fighting against Japan’s reckless acts of environmental destruction.”

In addition to a rally that was held in front of the National Assembly building in Yeouido on Wednesday attended by hundreds of registered party supporters, the Democratic Party said it will be holding a march from Seoul’s central Gwanghwamun Square to the presidential office in Yongsan district on Friday. Another rally attended by lawmakers and supporters is being planned on Saturday in Seoul.

On Thursday afternoon, 16 people, identified as college students by reports, were arrested after trying to break into the Japanese Embassy in Seoul, which has become a site for frequent rallies against the wastewater discharge.

After Japan announced the release on Tuesday, Democratic Party lawmakers staged a protest outside the Japanese Embassy and attempted to deliver a resolution calling on Tokyo to drop its plan entirely. The embassy declined to receive the resolution, which was signed by the entire party, according to the lawmakers.