South Korea conducted an annual military exercise on and around its easternmost islets of Dokdo earlier this week, sources said Friday, amid renewed tensions with Japan that has laid claims to the East Sea outcroppings.

The Navy, along with the Air Force and the Coast Guard, carried out the drill Tuesday, involving around eight vessels and five aircraft, including F-15K fighter jets, according to the sources.

The exercise was not made public in an apparent move to avoid aggravating tensions with Japan.

South Korea launched the Dokdo drills in 1986. Since 2003, it has typically conducted the training twice a year, usually in June and December, to better fend off possible foreign infiltrations to the rocky outcroppings and the surrounding waters.

In December, the military replaced the drill with a simulated command post exercise due to bad weather.

The latest drill took place two weeks after Japan repeated territorial claims to South Korea's islets in its latest annual diplomatic book.

Bilateral relations between Seoul and Tokyo have remained badly frayed since Japan enforced the export curbs last July, seen as retaliation against the South Korean Supreme Court's 2018 rulings that ordered Japanese firms to compensate Korean victims of forced labor.

As Japan has refused to lift the curbs, Seoul's trade ministry said Tuesday it will resume the dispute settlement proceedings with the WTO over the export curbs.

Earlier this week, a South Korean local court decided to start a procedure to forcefully sell off assets of a Japanese firm to compensate victims, which drew strong protests from Japan.

South Korea has been in effective control of Dokdo with a small police detachment since its liberation from Japanese colonial rule in 1945. (Yonhap)