Japan has filed a diplomatic protest with South Korea over trips by South Korean government officials to a remote set of small Pacific outcroppings both countries claim.
Japanese Foreign Minister Takeaki Matsumoto summoned the South Korean ambassador, Kwon Chul-hyun, to protest Wednesday against the visit by Seoul's gender and family minister and several other officials. The disputed territory is known as Dokdo in South Korea and Takeshima in Japan.
Japan and South Korea have long been at odds over ownership of the rocky markers between the Korean peninsula and Japan. Tokyo's claims have in the past sparked bitter protests in Seoul, where resentment against Japan's 1910-1945 occupation of the Korean peninsula remains palpable.
Early this year, the Japanese Coast Guard arrested a South Korean fishing boat captain near the isles. Officials in Seoul were quoted as saying the trawler appeared to have drifted into Japanese waters after an engine breakdown.
The area around the islets is a rich fishing ground, and mineral deposits are thought to lie beneath them.
The Japanese minister also said Wednesday Tokyo cannot accept visits this week by South Korean officials to another contested set of islands, known as the Kurils, which Japan claims, but Russia has occupied since the end of World War Two. The officials recently visited the islands using Russian visas.
Some information for this report was provided by AFP and Reuters.