TOKYO (AP) -- A Chinese airplane was spotted Thursday above small islands controlled by Tokyo but claimed by Beijing, the first time a Chinese aircraft allegedly violated airspace over the islands and the latest in a brewing territorial spat.
Japan levied a formal protest later in the day, but China said it was merely carrying out a normal operation.
The chief government spokesman said the Chinese plane entered Japanese air space in the morning. The Defense Agency said four Japanese F-15 jets headed to the area Thursday morning, but the Chinese plane, a Y-12, a nonmilitary type of aircraft, was nowhere to be seen by the time they got there. The Foreign Ministry said a formal protest was sent to the Chinese government through the embassy in Japan.
The islands known as Senkaku in Japanese and Diaoyu in Chinese have been at the center of a territorial dispute. The purchase of the islands by the Japanese government earlier this year from private Japanese owners set off massive anti-Japanese rallies in China.
"I want to stress that these activities are completely normal. The Diaoyu and its affiliated islands are China's inherent territory since ancient times," Chinese Foreign Ministry spokesman Hong Lei said of the plane. "China requires the Japanese side stop illegal activities in the waters and airspace of the Diaoyu islands."
It was the first time a Chinese plane entered Japanese air space over the disputed islands, as the two previous reported violations were by other nations, in 1979 by a Soviet plane and in 1994 by a plane from Taiwan, Defense Agency official Takashi Inoue said.
U.S. Assistant Secretary of State Kurt Campbell, while noting he did not yet know the specifics of the latest incident, urged calm, while noting the U.S. does not "take a position on the sovereignty of these islands."
"The security treaty between the United States and Japan applies to any provocative set of circumstances," he told reporters at the U.S. Embassy in Kuala Lumpur during an Asian tour. "We are encouraging all sides to take appropriate steps so that there will be no misunderstanding or miscalculation that could trigger an environment that would be antithetical to peace and stability."
Japanese ships have been patrolling the area around the islands in the East China Sea, on the lookout for approaching Chinese ships. Chinese ships have darted in and out the waters in that area in recent months.
Some analysts say China-Japan tensions are at their highest in years. Japanese exports have tumbled since relations soured.
Several candidates in the Dec. 16 parliamentary election are pushing for a more assertive and hawkish Japan, partly in response to the island controversy, including former Prime Minister Shinzo Abe, head of the main opposition Liberal Democratic Party.
Associated Press writers Louise Watt in Beijing and Eileen Ng in Kuala Lumpur contributed to this report. Follow Yuri Kageyama on Twitter at www.twitter.com/yurikageyama