By Kiyoshi Takenaka and Antoni Slodkowski
TOKYO (Reuters) - Three Chinese ships entered what Japan considers its territorial waters near disputed islands in the East China Sea on Monday, the Japanese government said, prompting an official protest and renewed diplomatic efforts to cool tensions.
The move comes a day after China called off celebrations to mark the 40th anniversary of the normalization of ties between the Asia's largest economies and as officials from China's ruling Communist Party, due to arrive in Tokyo on Monday, canceled their trip.
China's Xinhua news agency said two civilian surveillance ships were undertaking a "rights defense" patrol near the islands, citing the State Oceanic Administration, which controls the ships. One fishery patrol vessel was also detected inside waters claimed by Japan, the Japanese Coast Guard said.
Japan said it had lodged an official protest.
Sino-Japanese relations deteriorated sharply after Japan bought the islands, called Senkaku in Japan and Diaoyu in China, earlier this month, sparking anti-Japan protests in cities across China.
"In recent days, Japan has constantly provoked incidents concerning the Diaoyu islands issue, gravely violating China's territorial sovereignty," China's Xinhua news agency said.
The ship patrols were intended to exercise China's "administrative jurisdiction" over the islands, it said.
"Following the relevant laws of the People's Republic of China, (the ships) again carried out a regular rights defense patrol in our territorial waters around the Diaoyu islands."
The Japanese Coast Guard ordered the Chinese ships to move out of the area, but received no response, an official said.
In a move that could further complicate the issue, a group of Taiwanese fishermen said they planned to sail to waters near the islands later on Monday to reassert their right to fish there.
Self-ruled Taiwan, which China regards as a breakaway province, also claims the isles, located near rich fishing grounds and potentially huge gas reserves.
Sino-Japanese ties have long been plagued by China's memories of Japan's military aggression in the 1930s and 1940s and present rivalry over regional influence and resources.
Japanese Vice Foreign Minister Chikao Kawai will visit China on Monday to discuss Sino-Japanese relations with Chinese Vice Foreign Minister Zhang Zhijun, the Foreign Ministry said.
The latest flare-up in tensions comes when both countries focus on domestic political pressures. Japanese Prime Minister Yoshihiko Noda's government faces an election in months, adding pressure on him not to look weak on China.
China's Communist Party is preoccupied with a leadership turnover, with President Hu Jintao due to step down as party leader at a congress that could open as soon as next month.
Noda leaves for New York on Monday to take part in the annual gathering of the U.N. General Assembly, and attention will focus on whether he refers to the dispute.
Despite the long-running territorial row, economic ties between China and Japan have grown closer over the years and China is Japan's largest trading partner. In 2011, their bilateral trade grew 14.3 percent in value to a record $345 billion.
Tokyo's Nikkei China 50 index, composed of stocks of Japanese companies with significant exposure to the world's second-largest economy, shed 1.3 percent in morning trade on concerns over the dispute.
Bank of America Merrill Lynch said Japanese carmakers saw a 90 percent drop in showroom traffic and a 60 percent fall sales in the southern Chinese province of Guangdong, the largest market for Japanese brands, since the beginning of the anti-Japan protests.
(Reporting by Kiyoshi Takenaka, Antoni Slodkowski and Dominic Lau in Tokyo, Chris Buckley in Beijing and Jonathan Standing in Taipei; Editing by Chang-Ran Kim and Nick Macfie)
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