South Korean military said Thursday it would hold a rare live-fire drill near islets also claimed by Japan in a move likely to further raise diplomatic tensions with Tokyo.
The navy plans to hold the exercise near the Seoul-controlled chain of islets, called Dokdo by the South and Takeshima by Japan, on Friday, the defence ministry said.
"The navy plans to hold live-fire exercises near Dokdo tomorrow as part of its regular training," the ministry said in a statement.
Seoul's navy and coastguard have for years staged joint exercises near Dokdo but those do not involve live-fire drills.
Friday's naval drill is not part of the biannual exercises.
In Tokyo, the top government spokesman said that Japan had lodged an immediate protest.
"It is extremely regrettable," Chief Cabinet Secretary Yoshihide Suga told reporters. "Our country is strongly urging the South Korean government to cancel the exercise."
The rocky outcrops have been the subject of a bitter and decades-old territorial dispute between the two neighbours.
The row escalated in 2012 following a surprise visit by then South Korean President Lee Myung-Bak.
Tension escalated earlier this year after Japan moved to revise school textbooks to strengthen its historial claim to the islets.
Relations between the South and Japan are currently at their lowest ebb for years, mired in emotive disputes linked to Japan's 1910-45 colonial rule, including the islet dispute.
Many South Koreans believe Japan failed to properly atone for abuses carried out during the Japanese occupation.
The latest move by Seoul also came as Japan began a controversial review of its landmark 1993 apology over the use of many South Korean and Chinese women as wartime sex slaves for Tokyo troops.