The leader of South Korea's ruling Uri Party made a brief trip Monday to the South Korean-controlled islets also claimed by Japan, according to Yonhap News Agency.
"The Dokdo issue is not simply a matter of territory but a matter of history," Chung Dong Young was quoted as saying during his trip to the pair of rocky outcroppings known as Dokdo in South Korea and Takeshima in Japan.
"(South Korea) should sternly drive out Japan's attempt to turn it into an international territorial dispute. Koreans should defend Dokdo for themselves at any cost," he added, according to the Yonhap story.
In Tokyo, Vice Foreign Minister Shotaro Yachi said Japan will "file a protest as appropriate."
Senior Vice Foreign Minister Yasuhisa Shiozaki went to South Korea on Monday to hold talks with Foreign Affairs and Trade Minister Ban Ki Moon in a bid to mend ties following the recent dispute over the islets.
Yachi did not make clear if Japan would make the protest through Shiozaki.
The islets are located in the Sea of Japan in an area overlapped by both nations' claimed exclusive economic zones.
Chung's message appeared to echo South Korean President Roh Moo Hyun's address last week in which he said Japan's claim over the islets is tantamount to "justifying its history of crimes committed during the war of aggression."
Roh was apparently referring to Japan's invasion and occupation of the Korean Peninsula from 1910 to 1945.
Japan strained its poor bilateral ties with South Korea even further last month by trying to conduct a seabed survey in the area. South Korea responded by dispatching 20 gunships to block it.