Tokyo (AFP) - Japan warned Tuesday that China's "dangerous acts" over territorial claims in the East China Sea could lead to "unintended consequences" in the region, as fears grow of a potential military clash.

The annual defence white paper was adopted by hawkish Prime Minister Shinzo Abe and his ministers at a cabinet meeting, heaping criticism on Beijing's unilateral declaration of an Air Defence Identification Zone (ADIZ) late last year.

The ADIZ sparked regional criticism as well as condemnation from Washington, while commentators voiced concern over the growing chances of an armed conflict between the two Asian powers.

Tokyo's paper, which noted that China's military budget had quadrupled over the past decade, said Japan was seeing an "increasingly severe" security environment.

"Japan is deeply concerned about the establishment of 'the East China Sea ADIZ' which is profoundly dangerous act that... escalate the situation and may cause unintended consequences" in the region, the 505-page paper said.

Chinese vessels and aircraft have regularly approached an East China Sea archipelago claimed by both countries after Tokyo nationalised some of the chain in 2012, which is believed to harbour vast natural resources below its seabed.

The islands are called the Diaoyu by China and Senkaku by Japan.

In a June confrontation, Tokyo said that two Chinese fighter jets flew within 30 metres (100 feet) of its aircraft in an area where the two nations' air defence zones overlap.

Beijing responded that it was Japanese military planes that flew dangerously close to its aircraft.

China has also laid claim to much of the South China Sea, angering Vietnam, the Philippines and other Southeast Asian nations.

"In regard to conflicts over maritime interests, China has adopted assertive measures, including attempting to alter the status quo by coercive measures... which is incompatible with the existing international law and order," the paper said.

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"These measures include dangerous acts that could cause unintended consequences and raise concerns over China's future direction," it added.

- 'Serious destabilising factor' -

Tokyo's paper also warned that an unpredictable North Korea "repeatedly uses militarily provocative words and actions".

"Such military trends in North Korea constitutes a serious destabilising factor to the security not only of Japan but of the entire region and the international community," the paper said.

It briefly mentioned other territorial disputes including a row over Seoul-controlled islets -- called Dokdo by South Korea and Takeshima by Japan -- and the Russian-administered Kuril Islands, which Tokyo calls the Northern Territories.

"These territorial issues remain unsolved," it said.

Japan's military budget had been on the decline since 2002, but it took an upward turn, rising 2.2 percent in the current fiscal year, according to the paper.

Abe has vowed to boost spending on Japan's Self Defence Forces, with Tokyo last month loosening the bonds on its powerful military, proclaiming the right to go into battle in defence of allies.

The move was a highly controversial shift in the nation's pacifist stance.

Abe's government has also lifted a self-imposed ban on weapons exports.

His cabinet has agreed to spend 24.7 trillion yen ($240 billion) between 2014 and 2019 on various hardware, including drones, submarines, fighter jets and amphibious vehicles.