South Korea has strongly protested the Japanese government’s authorization of middle school textbooks that describe South Korea’s easternmost islets of Dokdo as Japanese territory.

While urging Tokyo to correct such descriptions immediately, Seoul stressed through a statement given by Foreign Ministry spokesman Cho Byung-jae that South Korea is firmly exercising sovereignty over the Dokdo islets, to which South Korean nationals always travel freely.

Seoul added that it will respond resolutely and firmly to any attempt by Japan to damage South Korea’s sovereignty over the territory.

While calling for a future-oriented partnership between Korea and Japan, Seoul also expressed deep regret over the authorization of textbooks that rationalize and whitewash incorrect attitudes towards history and urged a fundamental correction on the issue.

Earlier on Wednesday, Japan’s Ministry of Education, Culture, Sports, Science and Technology approved 12 editions of geography and social studies textbooks, all of which included Japan’s territorial claims over Dokdo.

The number of books that describe the islets as being illegally occupied by South Korea was found to have increased to four from one.

School boards are scheduled to decide whether to adopt the newly approved books in July and August. The new textbooks are expected to be used in Japan’s classrooms as of April next year.

Japan’s recent decision on the textbooks is expected to strain South Korea-Japan ties, which had warmed following South Korean support to Japan in the wake of the devastating earthquake and tsunami.