The government has put maritime police on alert after a group of Japanese right-wing activists announced their plan to land on Dokdo islets.

Citing information provided by the Tokyo government, the Foreign Ministry said the four Japanese men plan to depart from Shimane Prefecture Tuesday aboard a small boat for Dokdo in the East Sea.

The activists plan to stage a maritime demonstration and then attempt to land on Dokdo to highlight Tokyo's sovereignty claim over the rocky volcanic outcroppings.

A government official said Seoul would sternly deal with the men by seizing their boat and arresting them if they violate South Korea's territorial waters.

The islets have been at the center of a long-running dispute between the two countries. Seoul holds that the islets belong to South Korea, but that Japan began to claim sovereignty over them after it colonized the Korean Peninsula in the early 20th century.