Japanese air force jet scrambled around 200 times in the three months ending on Thursday compared with 114 times in the year-earlier period, he said. Detailed figures for the period will be announced next week.
"It appears that Chinese activity is escalating at sea and in the air," Admiral Katsutoshi Kawano, chief of the Japanese Self-Defense Forces, said at a regular press briefing in Tokyo.
Japan is embroiled in a dispute with China in the East China Sea over ownership of a group of islands which lie about 220 km (140 miles) northeast of Taiwan known as the Senkakus in Tokyo and the Diaoyu islands in Beijing.
Japan is worried that China is escalating its activity in the East China Sea in response to Tokyo's pledge to support countries in Southeast Asia, including the Philippines and Vietnam, that oppose China's territorial claims in the South China Sea.
Kawano said that Japan was "very concerned," about how China will react to a ruling by The Hague-based Permanent Court of Arbitration in a case brought by the Philippines on China's claims. The ruling is due on July 12.
Manila is contesting China's claim to about 90 percent of the South China Sea, arguing it violates the U.N. Convention on the Law of the Sea and restricts its rights to exploit resources within its exclusive economic zone.
China has refused to recognize the case.
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