South Korea conducted regular military drills to strengthen the defense of its easternmost islets of Dokdo last week, an informed source said Wednesday, amid lingering tensions caused by Japan's persistent claims to the East Sea outcroppings.

The country's military staged the drills to ensure their readiness to fend off potential foreign infiltrations to the rocky outcroppings, the source said without elaborating on the exact date and the size of the participating troops.

"(The military) held the exercise last week," the source told Yonhap News Agency on condition of anonymity.

Seoul's defense ministry and the Navy refused to confirm whether the drills took place.  

South Korea launched the Dokdo drills in 1986. Since 2003, it has conducted them twice a year.

In June, the country staged this year's first Dokdo drills. In protest, Tokyo called off a plan to hold a pull-aside meeting between President Moon Jae-in and then Japanese Prime Minister Yoshihide Suga on the margins of the Group of Seven gathering in Britain in the same month.

Dokdo has long been a recurring source of tension between the two neighbors, as Tokyo continues to make the sovereignty claims in its policy papers, public statements and school textbooks.

South Korea has been in effective control of Dokdo, with a small police detachment, since its liberation from Japan's 1910-45 colonial rule. (Yonhap)