South Korea summoned a senior Japanese diplomat on Tuesday and "strongly" protested Tokyo's reiteration of its claim to Seoul's easternmost islets of Dokdo in an annual defense paper released earlier in the day, officials said.
Seoul's foreign ministry said Japan's Cabinet approved the defense white paper for 2012 reiterating claims that Dokdo is Japanese territory historically and under international law.
"The Korean government strongly protests Japan's re-inclusion of territorial claims to Dokdo, which is clearly indigenous territory of Korea in terms of history, geography and international law, in the Defense of Japan 2012 issued on July 31," ministry spokesman Cho Tae-young said in a statement.
South Korea "urges the Japanese government to take immediate corrective measures," Cho said.
The ministry called in Kurai Takashi, Japan's deputy chief of mission in Seoul, and lodged the protest, ministry officials said.
"The Korean government once again makes clear the plain fact that Dokdo is an indigenous territory of Korea over which it exercises full territorial sovereignty, and that it will not tolerate any unjust claim of Japan to the territory," Cho said.
Dokdo, which lies closer to South Korea in the body of water that divides the Korean Peninsula and Japan, has long been a thorn in relations between the two countries. South Korea keeps a small police detachment on the islets, effectively controlling them.
South Korea rejects Japan's claim to Dokdo as nonsense because the country regained its independence from Japanese colonial rule and reclaimed sovereignty over its territories, including Dokdo and many other islands around the Korean Peninsula.
The latest reiteration of claims to Dokdo by Japan is expected to further strain ties with South Korea at a time Seoul is pressing Tokyo to resolve the issue of aging Korean women who were forced into sexual slavery for Japan's World War II soldiers.
Japan has refused to do so, saying the matter was already settled by a 1965 treaty that normalized relations between the two countries.
The bilateral relations hit a rough spot again in June, when Seoul postponed the signing of a military intelligence-sharing pact with Tokyo at the last minute because of strong political outcry in South Korea as Japan has shown no signs of sincerely working to resolve its wartime atrocities.
Japan ruled the Korean Peninsula as a colony from 1910 to 1945 and bitter memories about its brutal rule still linger.