Jan. 4 (Bloomberg) -- China has drilled at the Tianwaitian gas field in the East China Sea, breaching an agreement with Japan last year that the two nations’ governments would continue talks on joint development, the Sankei newspaper said.

Japan has protested against the drilling, the report said, citing government sources it didn’t identity.

Japan and China agreed in June to jointly develop the disputed natural gas fields and to cooperate in exploration of the East China Sea.

To contact the reporter on this story: Masumi Suga in Tokyo at msuga@bloomberg.net.

Last Updated: January 3, 2009 21:15 EST