President Moon Jae-in has instructed South Korean government officials not to sit idle on Japan's territorial claims over Dokdo and potential release of radioactive water into the Pacific Ocean, an informed source said Tuesday.

His call came amid unrelenting trade and diplomatic disputes between the neighboring countries. Tokyo started the fight with export restrictions, and Seoul hit back with similar retaliatory measures.

Adding to the uproar among South Koreans over Japan's export curbs, apparently introduced over long-festering historical issues, it was revealed that the torch relay map and related materials on the official website of the 2020 Tokyo Olympics and Paralympics show Dokdo as Japanese territory.

Dokdo is South Korea's easternmost islets, and the country is responding strongly to what it views as a provocation regarding its sovereignty over the islands.

Moon mentioned the issue in recent meetings with senior government officials, according to the source. He also talked about reports of the possibility that the utility company operating Fukushima's tsunami-devastated nuclear power plant will discharge contaminated water into the sea to deal with a shortage of on-site storage.

The president instructed related agencies such as the Ministry of Foreign Affairs and the Ministry of Culture, Sports and Tourism to deal with the problem actively and properly. He said there was a need for coordination with international organizations, the source said.

The Korean Sport & Olympic Committee said it has sent a protest letter to the International Olympic Committee and the Japanese Olympic Committee with regard to the Dokdo issue.

The foreign ministry said it will keep a close watch on Japan's handling of the radioactive water.

"Our government puts top priority on the health and safety of our citizens, and we plan to actively ask Japan to disclose information and to provide us with a concrete stance on the current management system and disposal plans," ministry spokesman Kim In-chul told reporters. (Yonhap)