Japan plans to lodge an official protest with China over its continued oceanographic surveying in Japan's exclusive economic zone around Okinotori Island, government sources said Sunday.

Japan urged China at a working-level meeting in Beijing on April 22 to stop the surveys, but Chinese officials claimed the surrounding waters cannot be regarded as an exclusive economic zone "because Okinotori Island is not an island but rocks."

Under the United Nations Convention on the Law of the Sea, all marine scientific research in an exclusive economic zone is subject to the consent of the coastal state, which has sovereignty over natural resources and certain economic activities within a 200-nautical mile zone of its territory's coastline.