A South Korean ship departed on Sunday on its way to survey waters near Seoul-held islands claimed by Japan, an official said, in a move that threatened to raise tensions with Tokyo.
South Korea announced last week its plan to conduct a survey of waters near islets known as Dokdo in Korean and Takeshima in Japanese, despite Tokyo's protests. The survey was to start on Monday and last until July 14.
Park No-jung, an official from the Ministry of Maritime Affairs and Trade, said the 2,533-ton 'Haeyang 2000' left the port of Busan on Sunday night with some 20 crew members.
The boat, however, was staying in waters near Busan for now and it was uncertain when it would head toward the disputed islands, Park said.
Yonhap news agency reported the South Korean coast guard planned to escort the ship on the survey, presumably to ward off any Japanese interference. The coast guard did not immediately answer phone calls to confirm the report.
The tiny islets, about equidistant between Japan and South Korea, are held by Seoul but claimed by Tokyo. South Korea resents Japan's claim to the islands as a legacy of Tokyo's 1910-1945 colonization of the Korean peninsula, and fiercely protested earlier this year when Tokyo announced it would conduct its own survey of the waters.
Japan scuttled the survey in the face of South Korean protests, which included the dispatch of patrol boats to the islets and veiled warnings the survey could lead to a clash.
Talks between the two sides in Tokyo this month on the island row made no progress. Last week, Japanese Chief Cabinet Secretary Shinzo Abe called for "self-restraint" when asked about the imminent South Korean survey.
Ownership of the islands are central to the two countries' dispute over the demarkation of their exclusive economic zones in the resource-rich waters. Each side sees a maritime survey by the other as a way of formalizing its claim.
Under international law, each country has rights to explore and use marine resources within 200 nautical miles (230 miles; 370 kilometers) from its shores. Japan and South Korea both claim the islands fall within their territory.
Japan's Yomiuri newspaper reported Saturday that the head of the Japanese coast guard suggested Tokyo would not to attempt to seize South Korean ships in the event of a survey.
The paper also reported that a top Japanese foreign ministry official said Tokyo would conduct its own survey unless Seoul backs off its plans.