Tensions between Beijing and Tokyo flared again yesterday after 168 Japanese lawmakers visited a Tokyo war shrine and both countries sent ships to a disputed area of the East China Sea.
Japanese Prime Minister Shinzo Abe warned Tokyo would "expel by force" any Chinese landing on the Diaoyu Islands, known as the Senkakus in Japan, while Beijing accused Tokyo of showing no respect for history.
Abe's warning came after China sent eight surveillance vessels within 12 nautical miles of the islands - the most in a single day since Japan bought three of the islands in September.
Beijing said they were sent to monitor Japanese fishing boats.
The State Oceanic Administration said the fleet "collected evidence of the Japanese vessels' infringement upon China's sovereignty". In response, Abe told lawmakers that Japan would take "decisive action" against any attempt to enter Japanese territorial waters.
"It would be natural for us to expel by force if the Chinese were to make a landing," he said.
Tokyo summoned Chinese ambassador Cheng Yonghua . Cheng, in return, demanded that all Japanese ships leave the waters near the islands.
Relations have been troubled since September, when Beijing described Japan's "nationalisation" of the islands as a "farce".
Both sides stepped up patrols, but tensions eased when attention switched to concerns over North Korea's nuclear threats.
Da Zhigang , an expert in Japanese affairs at the Heilongjiang Academy of Social Sciences, said: "The latest spat will trigger public sentiment in China, which will push the Chinese leadership to be tougher against Japan, making it difficult to lower tensions." A non-partisan group of 168 Japanese lawmakers yesterday visited the Yasukuni Shrine, which glorifies Japan's wartime past, after three cabinet ministers paid homage there at the weekend.
Liberal Democratic Party member Hidehisa Otsuji said the visit was a "natural act".
But in Beijing, Foreign Ministry spokeswoman Hua Chunying said Japan was trying to deny its "history of aggression".
South Korean Foreign Ministry spokesman Cho Tai-Young also condemned the visit, saying Tokyo should "think hard" about its impact on countries that suffered wartime occupation.
Professor Lian Degui , of the Shanghai Institutes for International Studies, said Tokyo wanted to see if Beijing would tone down its rhetoric while handling the Sichuan quake.
Abe offered help, but Beijing said overseas assistance was not needed. "It shows that Beijing is still being tough," Lian said.
Additional reporting by Agence France-Presse