TOKYO: Japan said on Tuesday (Jul 15) that China's intensifying military activities could "seriously impact" its security, citing the first confirmed incursion by a Chinese military aircraft into its airspace in an annual threat assessment.The defence ministry said in its white paper that China was ramping up its activities in the entire region surrounding Japan.A Chinese military aircraft entered Japan's airspace in August last year, it said. Then, in September, a Chinese aircraft carrier and two other naval ships sailed between two Japanese islands near Taiwan.Beijing's military "created a situation that could seriously impact Japan's security", the paper said.It repeated its comment from last year's paper that China's military ambitions pose "an unprecedented and (the) greatest strategic challenge" to Japan and the world.Beijing responded by saying the paper "hypes up the so-called China threat"."China expresses strong dissatisfaction and firm opposition to this and has lodged solemn representations with Japan," China's foreign ministry spokesman Lin Jian said.Tokyo said last week that Chinese fighter jets flew within 30m of a Japanese military patrol aircraft over the East China Sea.Last year, Chinese vessels sailed near the Japanese-administered Senkaku islands - known as the Diaoyu in China - a record 355 times, according to Tokyo.And last month, Japan said that two Chinese aircraft carriers sailed in the Pacific simultaneously for the first time, including in Japan's economic waters.China called it "routine training".Beijing has also conducted joint drills with Russia which are "clearly intended as a demonstration of force against Japan", the paper said.It repeated that North Korea's activities pose a "more grave and imminent threat to Japan's national security than ever before".The white paper was approved by the cabinet of Prime Minister Shigeru Ishiba on Tuesday.