The exercises come days after North Korea tested a series of short-range projectiles, and are reportedly a precursor to annual maritime drills near a set of disputed islands that risk adding to trade tensions with Tokyo.

The protest to Hisashi Michigami, minister at the Japanese embassy in Seoul, followed the event in Matsue, the capital of the western Japan prefecture of Shimane, on Saturday, attended by Yoshitami Kameoka, parliamentary secretary with the central government's Cabinet Office.

A Japanese scholar has branded as "childish" the reactions in South Korea and China to new school textbooks that describe disputed islands as Japanese territory. Japan's Education Ministry on Tuesday approved a range of new textbooks for the school year that starts in April next year, with two geography books and six covering politics and economics stating that the Diaoyu, or Senkaku, islands and the Takeshima islands, which South Korea calls Dokdo, belong to Japan.

Beginning this year, all schools will be required to provide a minimum of 10 hours of classes annually on "the importance of Dokdo", a ministry spokesman said.