"[These islands are] an inherent territory of Japan in light of historical facts and international law ... [such a visit] is unacceptable," Kanasugi said at a meeting with Kim Kyung Han, a political minister at the South Korean Embassy in Japan, as quoted by the Kyodo news agency.
Earlier in the day, a group of South Korean lawmakers visited the country's easternmost islets, known as Dokdo in South Korea and Takeshima in Japan, and urged Tokyo to cancel its trade restrictions against the Asian neighbor.
The Liancourt Rocks islands lie almost equidistant from the two states. They have been administered by Seoul since 1954, a claim Japan disputes. Tokyo has suggested that Seoul should present the issue to the International Court of Justice. However, South Korea believes there is no dispute over the islands and considers them to be its territory historically, geographically and legally.
The relations between Japan and South Korea dampened last year after the latter's top court ruled that a number of Japanese companies could be sued for their use of forced labor during World War II. Japan has protested the decision, claiming that the 1965 agreement between the two countries had resolved the issue of damages once and for all.
The ties became even more tense in July, when Japan canceled preferential treatment for the exports of fluorinated polyimides, photoresist and hydrogen fluoride, which are vital for the production of semiconductors and displays, to South Korea.
In August, Tokyo decided to remove Seoul from the list of trade partners that have preferences in importing Japanese technologies and high-tech products from August 28. Seoul retaliated by excluding Japan from its list of favored trade partners with facilitated export conditions.