SEOUL — A group of opposition lawmakers from the Republic of Korea departed for Japan on Monday to protest its planned discharge of radioactive wastewater from the crippled Fukushima nuclear power plant into the ocean.

Nine lawmakers of the main opposition Democratic Party and two liberal independents flew to Japan earlier in the day for a three-day trip, according to the Democratic Party.

The lawmakers were quoted by Yonhap News Agency as saying at the airport before their departure that they would meet with politicians, experts and civic activists in Japan to strengthen their solidarity struggle and promote the ROK's opposition to the nuclear-contaminated water release through the international media.

They vowed to do their best to prevent the Fukushima wastewater discharge through international cooperation.

After arriving in Tokyo, the lawmakers held a protest rally in front of the residence of Japanese Prime Minister Fumio Kishida in cooperation with local civic activists.

The ROK lawmakers also planned to make a protest visit to the International Atomic Energy Agency Regional Office in Tokyo and hold a sit-in protest in front of the National Diet.

China's Foreign Ministry spokeswoman Mao Ning said on Monday that the Japanese government is being selfish and irresponsible for pushing ahead with ocean discharge of nuclear-contaminated water in spite of strong opposition from both home and abroad.

Noting that the International Atomic Energy Agency's Director-General Rafael Mariano Grossi has more than once said the institution will not endorse Japan's ocean discharge, the spokeswoman urged Japan not to use the report as a green light for dumping such water.

Wang Qingyun in Beijing contributed to this story.