South Korea's military launched an annual drill on Tuesday near the disputed Dokdo islets, local media reported.
The drill, dubbed the East Sea Territory Protection Exercise, is being staged despite Japan's protest, according to Yonhap News Agency.
Involving the Navy, Air Force and Coast Guard, the war game "is aimed at responding to threats to our territory, people and properties," the agency reported citing a Navy official.
Seoul has held drills near the islets, located between it and Japan, every year since 1986.
During a recent G7 meeting in the UK, Tokyo called off an agreed meeting between South Korean President Moon Jae-in and Japanese Prime Minister Yoshihide Suga to protest the planned drill around the islets.
South Korea effectively controls the islets, which Tokyo refers to as Takeshima and claims as Japanese territory.
Meanwhile, Seoul conducts two drills around the islets every year, usually in June and December.
Diplomatic relations between the two countries have remained at an all-time low over the past year after a South Korean court ordered Japanese firms to compensate victims of forced labor during Japan's colonial rule over the peninsula.
*Writing by Islamuddin Sajid
