China has decided to postpone a negotiation with Japan on the East China Sea issue as part of its response to the seizure of a Chinese fishing boat, said Foreign Ministry spokeswoman Jiang Yu Friday night.

The postponed talks, the second governmental negotiations on the principle common understandings on the East China Sea issue, had been scheduled for mid September, according to Jiang.

A Japanese court on Friday, despite Chinese protests, ruled a 10-day detention through Sept.19 against the captain of a Chinese trawler which collided with Japanese patrol ships off the Diaoyu Islands in the East China Sea on Tuesday.

"The Japanese side has ignored China's repeated solemn representations and firm opposition, and obstinately decided to put the Chinese captain under the so-called judiciary procedures. China expresses strong discontent and grave protest," Jiang said.

"The Diaoyu islands and its adjacent islets have been Chinese territory since ancient times. Japan's acts have violated the law of nations and basic international common sense, and are ridiculous, illegal and invalid," Jiang said.

"Japan will reap as it has sown, if it continues to act recklessly," Jiang warned.

Chinese Foreign Minister Yang Jiechi on Friday summoned Japanese Ambassador to China Uichiro Niwa, saying China's determination to defend its sovereignty over the Diaoyu Islands and the interests of the Chinese people was unswerving.

Yang said China demanded Japan immediately and unconditionally release the boat and all the crew, including the captain.

On Tuesday, two Japan Coast Guard patrol ships and the Chinese fishing boat collided in waters off the Diaoyu Islands.

No injuries were reported, but the fishing boat was then intercepted by the Japanese patrol.