South Korea's Ministry of National Defense called a Japanese Embassy military attache in Seoul to denounce and protest Japan's sovereignty description of the Liancourt Rocks in a defense White Paper, The Korea Times reported.
The Sea of Japan islets -- known as Dokdo in Korean and as Takeshima in Japanese -- have been controlled by South Korea since 1954.
They lie in rich fishing grounds that could also contain large gas deposits.
Calling Japan's claim to the islets "colonial" and suggesting the act could hurt South Korean-U.S. relations, the government "urged Japan to take corrective measures on Dokdo, which is South Korea's territory from the perspectives of geography, history and international laws," said Song Bong-heon, head of the South Korean ministry's international cooperation bureau.
Japan had no immediate comment.