Japan said Friday it had lodged a protest with South Korea over military drills conducted in waters near a pair of islets in the Sea of Japan, claimed by both countries.

Takehiro Funakoshi, director general of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, told Kim Yong Gil, a minister at the South Korean Embassy in Tokyo, that the drills, reportedly held on Thursday, were "totally unacceptable" and "extremely regrettable," according to the Japanese ministry.

The South Korea-controlled Dokdo islets, known as Takeshima in Japan, are seen from a ferry in August 2019. (Getty/Kyodo)

The ministry quoted Funakoshi as saying the islets are an integral part of Japanese territory in light of historical facts and based on international law.

Citing an informed source, Yonhap News Agency reported earlier Friday that South Korea had conducted "regular military drills" in waters to enhance the defense of the islets controlled by Seoul, which are called Dokdo in South Korea and Takeshima in Japan.

Yonhap also said the drills followed "Japan's renewed claims to the East Sea outcroppings" in the Japanese government's National Security Strategy, revised a week ago for the first time in nine years.

South Korea conducts the drills about twice a year.