"The Navy carried out the annual exercise aimed at safeguarding the East Sea territory," the source told South Korea's Yonhap news agency.
According to the agency, the drills were scaled-down compared to those conducted in August, which had mobilized roughly 10 vessels and 20 aircraft, in an apparent effort to avoid making its relationship with Japan more strained.
Tensions between the two countries began to rise earlier in the year after Japan introduced export restrictions in an apparent response to a South Korean court ruling that ordered Japanese companies Nihon Steel, Fujikoshi Corporation and Mitsui Havy Industries to pay reparations for their use of forced labour during World War II. The countries have since been seeking a way to overcome their differences, including through negotiations on trade policies. To that end, South Korean President Moon Jae-in and Japanese Prime Minister Shinzo Abe met in the Chinese city of Chengdu on Tuesday.
South Korea has been conducting military drills near the southernmost Liancourt Rocks for over thirty years. Since 2003, they have been held biannually.
The Liancourt Rocks islands also referred to as Dokdo by South Korea and Takeshima by Japan, lie almost equidistant from the two states in the Sea of Japan. They have been administered by Seoul since 1954, a claim Japan disputes. Tokyo has suggested that Seoul should present the issue to the International Court of Justice, but South Korea believes there is no dispute over the islands and considers them to be its territory historically, geographically and legally.