About 20 Japanese lawmakers, including a senior government official, joined a ceremony Friday, commemorating the day the islands at the centre of a dispute with South Korea came under Japan's jurisdiction 108 years ago.
Aiko Shimajiri, a parliamentary secretary with the Cabinet Office, attended the annual ceremony called Takeshima Day in Shimane prefecture, western Japan.
The islands are controlled by South Korea where they are known as Dokdo, but are also claimed by Japan, where they are known as Takeshima.
South Korea slammed Japan for holding the ceremony and urged it to drop the "unjustifiable and meaningless" arguments, the Yonhap News agency reported.
In August, South Korean President Lee Myung Bak's trip to the islands sparked strong protests from Japan.
It was the first visit to the islets by a South Korean president since the territorial dispute surfaced decades ago.