The Japanese government has lodged a protest with China over its apparent test drilling in a gas field near the 2 countries' median line in the East China Sea.
Japan and China in 2008 agreed to jointly develop the region's gas fields. While negotiations for a related treaty remain stalled, China has unilaterally continued to develop the fields, including building structures near the median line.
The Japanese Foreign Ministry says Japan has learned that a Chinese ship was engaged in what appeared to be experimental drilling for resources on the Chinese side of the median line in mid-November.
Chief Cabinet Secretary Yoshihide Suga told reporters on Monday that it is extremely regrettable that China has continued to unilaterally develop the gas fields despite Japan's repeated requests to stop. He added that the 2 countries have yet to establish a marine boundary in the East China Sea.
Suga also said the leaders of Japan and China have said they would work toward resuming negotiations soon on implementing the agreement to jointly develop resources in the East China Sea.
He added that the government will continue to strongly urge China to resume the talks.