Japan called North Korea's nuclear and missile development a "grave and imminent threat" to the region and international security, and criticized China's increasingly assertive military action as "dangerous" in its annual defence report.

The report, approved Tuesday by the cabinet, comes as Prime Minister Shinzo Abe's government pushes for Japan to take on greater military roles abroad. This year's 484-page report allocated several more pages to each country than the previous one.

It cited North Korea's technological advances in recent nuclear tests and says Pyongyang might have achieved the capability to miniaturize atomic weapons and develop warheads.

"North Korea's military activity has increased tensions on the Korean Peninsula, and become a grave and imminent threat not only to Japan but also to the security in the region and the international society," the report said. It reiterated concerns that North Korean may have acquired a missile capable of launching as far as 10,000 kilometres.

The report called China's reclamation moves in the South China Sea a provocation, and urged Beijing to accept a recent international arbitration ruling.

It said China's escalating activity in the East China Sea caused Japan to scramble against Chinese warplanes more than 570 times last year.

The report said China has stepped up activity around Japan-controlled islands that Beijing also claims, adding that a Chinese warship entered a strip of water just outside Japanese claimed waters in the area.

China's navy has fired dozens of missiles and torpedoes during exercises in the East China Sea that come amid heightened maritime tensions in the region, underscoring Beijing's determination to back up its sovereignty claims with force if needed.

The live-fire drills that began Monday follow China's strident rejection of an international arbitration panel's ruling last month that invalidated Beijing's claims to a vast swath of the South China Sea.

That led to days of angry statements from Beijing, followed by live-firing naval exercises in the South China Sea and the launch of regular aerial patrols in the area.

China's Supreme Court said on Tuesday people caught illegally fishing in Chinese waters could be jailed for up to a year, issuing a judicial interpretation defining those waters as including China's exclusive economic zones.

China's actions over conflicting maritime claims are unilateral and high-handed, and some of them are "dangerous actions that could trigger unanticipated situations," the Japanese report said. "They raise strong concern about what may happen in the future."