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, repeating earlier comments that China’s actions were of “grave concern”.
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.
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 morning.
Japan is in a multi-year process of increasing its defence spending to the Nato standard of roughly 2% of gross domestic product (GDP).
It is bolstering its military ties with Washington – and other regional US allies – to make US and Japanese forces nimbler in response to threats such as a Chinese invasion of Taiwan.
The Pentagon is pressing Japan and Australia to make clear what role they would play if the US and China went to war over Taiwan, the Financial Times reported on Saturday.
Elbridge Colby, US under-secretary of defence for policy, has been pushing the issue in meetings with Japanese and Australian defence officials in recent months, the FT said.
Colby said on X that president Donald Trump’s “common sense agenda” included “urging allies to step up their defence spending and other efforts related to our collective defence”.
“Of course, some among our allies might not welcome frank conversations,” Colby added.
The issue also forms part of negotiations between Tokyo and Washington on a trade deal to avert 25% tariffs on Japanese imports due from Aug 1.