TOKYO — Japan lodged a protest with China after Beijing installed a mobile offshore drilling rig on its side of the median line in the East China Sea, where Tokyo suspects it is conducting exploratory drilling for a natural gas field, sources familiar with the matter said Monday.
Japan filed the protest Friday after the Japan Ministry of Defense discovered in late June that the drilling rig had been fixed to the seabed about 400 kilometers northwest of Okinawa’s main island, the sources said.
Japan and China maintain overlapping claims in the East China Sea. Tokyo considers the median line the de facto boundary between the two countries’ exclusive economic zones, while Beijing maintains that its continental shelf extends farther east toward Okinawa, giving it rights to a broader maritime area.
Japan has called on China to resume negotiations under a 2008 agreement on the joint development of natural gas resources in the East China Sea. The agreement has not been implemented.
The latest protest comes as Japan continues to raise concerns over China’s maritime activities, including coast guard patrols, military operations and offshore resource development.
Japan also lodged a protest on June 22 after detecting another Chinese mobile drilling vessel anchored in the East China Sea.
