Seoul has "strongly" protested against a Japanese defence report for describing South Korea-controlled islets in the Sea of Japan as Japanese territory.
The annual Japanese defence white paper adopted by the cabinet said that the disputed three islands, known as Dokdo in South Korea and Takeshim in Japan, are historically Tokyo's land under international law.
The South Korean foreign ministry summoned Kurai Takashi, Japan's deputy chief of mission in Seoul, and lodged the protest on Tuesday, South Korea’s Yonhap news agency reported.
The group of rocky outcroppings lying between the two nations has been a source of diplomatic tension between Japan and South Korea for years.
"Dokdo is clearly South Korean territory historically, geographically and under international law, and there is no dispute over its sovereignty," South Korean defence ministry deputy spokesperson Wee Yong-sub said in a public statement condemning the report.
He added that should the claim not be withdrawn, South Korea-Japan defence exchange and cooperation would suffer.
The Japanese government discourages its citizens from visiting the islands, saying that such visits might acknowledge South Korea's jurisdiction over the islands, which it disputes.
|Al Jazeera's Harry Fawcett reports from Seoul
Tokyo has long laid claim to the islets in school textbooks, government reports and through other avenues, stoking enmity in South Korea against its former colonial ruler.
South Korea views the claims as a sign that Japan has not fully repented for its imperialist past and stations a small contingent of police officers on the disputed islands in a show of control.
Seoul says that the islands were annexed by Japan in 1905 before the country colonised the Korean peninsula. According to South Korea, they were restored to Seoul after World War II.
Japan says, however, it established sovereignty over the islands by the mid-17th century, as Japanese sailors used it as “docking point for ships and a rich fishing ground".
A South Korean coastguard detachment has been stationed there since 1954.
The same Japanese defence paper also said that China's "coercive" behaviour in waters around another set of disputed islands could trigger an incident.
"China ... has taken action described as coercive, which includes risky behaviour," the report said.
Tokyo took three of the five Senkaku islands out of private ownership in September. Beijing lays claim to the islands, and calls them the Diaoyus.
"China's activities include its intrusion into Japan's territorial waters, its violation of Japan's territorial airspace and even dangerous actions that could cause a contingency," the report said.
In particular, the paper said a Chinese frigate locked weapons-targeting radar on a Japanese destroyer in January - a claim Beijing has denied.
"These acts are extremely regrettable and China should accept and stick to the international norms," it added.
Japan is currently considering changing its pacifist constitution and the role of its Defence Force, and debating acquiring the capability to attack enemy targets.
Chinese and Japanese ships have for months traded warnings over intrusions into what both governments regard as their sovereign areas around the islands, which are strategically sited and rich in resources.
Chinese ships have regularly sailed into the 12-nautical mile territorial waters of the islands, where they are confronted by Japan's well-equipped coastguard.