BEIJING (Kyodo) China warned Japan Thursday against responding, as it hinted it might, to the start of gas production by a Chinese consortium in the East China Sea.

Chinese Foreign Ministry spokesman Qin Gang also criticized Foreign Minister Taro Aso for expressing displeasure at the rise in trade between China and North Korea, saying his comments "go against diplomatic common sense."

Qin said Chinese gas development projects in the East China Sea are being conducted in waters not disputed by the two countries, adding that any action taken to inhibit them could constitute a violation of China's sovereign rights, depending on their nature.

China has been tapping the gas fields, including one called Chunxiao, which Chinese newspapers have said could begin full-scale production by the end of March. Japan calls the field Shirakaba.

Although the gas fields are on the Chinese side of the median line proposed by Japan to define the boundaries of the two countries' overlapping exclusive economic zones, Tokyo is worried that the proximity of the drilling to the line may allow China to siphon off resources that lie under the seabed in the area claimed by Japan.

Qin's statement was in response to Aso's comments Wednesday suggesting Japan might take countermeasures if gas production starts.

Aso did not elaborate on what steps Japan might take, but one possible response would be to start test-drilling on the Japanese side of the median line.

China does not recognize the median line, saying the demarcation of the countries' exclusive economic zones should follow "continental shelf" principle, which would give Beijing rights to resources right up near Okinawa and encompassing Taiwan.

"If Japan takes one-sided action in a disputed area, that would constitute a violation of China's sovereign rights and we are firmly against this," Qin said.