Japan has lodged a protest with South Korea over its reported plan to conduct a military drill around a pair of Seoul-controlled, Tokyo-claimed islets in the Sea of Japan, Foreign Minister Fumio Kishida said Friday.

The drill, which will start Monday, "is unacceptable in light of our country's stance regarding the sovereignty of Takeshima," Kishida told reporters, referring to the islets known as Dokdo in South Korea. "It is regrettable."

Kenji Kanasugi, head of the Foreign Ministry's Asian and Oceanian Affairs Bureau, lodged the protest Wednesday with a senior diplomat at the South Korean Embassy in Tokyo, a Japanese government source said.

The South Korean military conducts training exercises near the rocky outcroppings a few times a year. In December, about 10 South Korean Marines landed on one of the two islets, prompting Japan to lodge a strong protest.

The drill comes as the relationship between Japan and South Korea remains strained by the long-standing "comfort women" issue. The term is Japan's euphemism for the females forced to work in Japanese military brothels before and during the war.

Japan has said the erection of statues symbolizing the women in front of Japanese diplomatic facilities in South Korea, including one in December, goes against the spirit of a 2015 bilateral agreement to "finally and irreversibly" resolve the protracted dispute over the issue.

The re-emergence of a statue that was reportedly taken down when it first appeared outside the Japanese Consulate in Busan in December prompted Tokyo to recall its ambassador. Opponents in South Korea have meanwhile criticized the accord for not fulfilling their key demand that the Japanese government admit legal responsibility for compensation.