Japan scrambled fighter jets after 11 Chinese military planes flew near southern Japanese islands during what Beijing said was a drill to improve its long-range combat abilities.
The planes - eight bombers, two intelligence gathering planes, and one early-warning aircraft - flew near Miyako and Okinawa on Friday without violating Japan's airspace, its defence ministry said in a statement.
Chinese air force spokesman Shen Jinke said several types of planes were involved in the manoeuvres over the western Pacific, the state-run Xinhua news agency reported.
Shen said such open-sea exercises had improved its military's long-distance combat abilities.
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While there was no further comment from the Japanese defence ministry, the Yomiuri Shimbun newspaper reported it was "unusual" for China to dispatch such a large fleet close to Japan's airspace.
The defence ministry was analysing the purpose of China's mission, it said.
Japan scrambles fighter jets hundreds of times a year to defend its airspace with Russian and Chinese aircraft often in the area.
Beijing warned this has heightened tensions between the two Asian powerhouses, which are already at loggerheads over a long-standing territorial dispute in the East China Sea.