Japan has lodged repeated protests with China for continuing exploration work at one of the disputed gas fields in the East China Sea, saying it violates a deal struck in June, sources knowledgeable about the bilateral relationship said Sunday.
But China issued a statement Sunday saying it is within Beijing's right to develop the gas field, known as Tianwaitian in China and Kashi in Japan.
Japan filed the protests last year after it confirmed development activities in the gas field that lies in an area subject to further discussions between the two countries under the June deal, the sources said.
Chinese Foreign Ministry spokesman Qin Gang said China sees no problem in continuing work in the gas field, although he did not confirm that activities were ongoing.
"Gas fields such as Tianwaitian are located in waters controlled by China that are not under dispute," the statement said. It was posted on the ministry's Web site after the Sankei Shimbun first reported about China's activities there.
"China's development activities in such gas fields constitute the exercising of its sovereign right," the statement went on.
The field lies just west of the Japanese-claimed median line, and Tokyo says that exploration of the gas field may siphon off resources from Japan's side.
The June agreement was a breakthrough toward solving the long-standing dispute between the two countries over gas exploration projects in the East China Sea.
The two countries agreed to jointly explore a 2,700-sq.-km area south of the Asunaro gas field, which China calls Longjing, located near the median line.
Beijing has welcomed investment by Japanese corporations to develop the Chinese-operated Chunxiao gas field, also near the median line and known as Shirakaba in Japan.