The annual defense paper, approved Friday by the Cabinet, underscores Japan's fear of being targeted by its neighbor. Its reaction to the North's recent tests contrasts to the low-key U.S. response.
"Taking into consideration its technological maturity acquired by nuclear tests, North Korea seems to have already achieved miniaturization of warheads to place atop ballistic missiles," said the report, which last year only mentioned it as a possibility. The North is now aiming to further increase missile ranges, improve accuracy and operational and surprise attack capability and diversify launching methods, it said.
North Korea's military activity "still poses serious and imminent threat" to Japan's security as well as international peace and safety.
Since the second U.S.-North Korea summit collapsed this year, North Korea has fired 10 short-range missiles and projectiles deemed new and upgraded.
Citing its analysis, the Defense Ministry said they were three new types, including one resembling Russia's Iskander, and flight distances ranging from 200 kilometers (124 miles) to 600 km (370 miles). It said the missiles were new and their capability upgraded, and that Japan needs to further strengthen its missile defenses.
North Korean missiles within those flight ranges could strike targets in Japan and South Korea but not the U.S., which has been the basis for the low-key Trump administration reaction.
Japan's defense report also noted China's threat is expanding into space from the regional seas, saying Japan must prioritize space security.
Japan has been bolstering its defense role under its alliance with the U.S. and is now launching a space unit and measures against cyber and electromagnetic attacks.
While many countries are developing their capabilities to ensure their military superiority, China and Russia have been enhancing capabilities to "impede the U.S. and its allies from using outer space," the report said. It said China and Russia are developing missiles and satellites to destroy satellites or interfere with their communication with the ground. "Threats to stable use of the space are intensifying," it said.
Even though Japan and South Korea are U.S. allies who face shared threats, the defense report gave South Korea a relegated position. Their relations deteriorated rapidly since July over wartime history and export controls that spilled over to defense, prompting Seoul to announce in late August it would terminate a bilateral military intelligence pact. In the report, Japan urged Seoul to "wisely respond to secure appropriate cooperation between Japan and South Korea, and among Japan, the U.S. and South Korea."
The intelligence sharing pact had symbolized the countries' three-way security cooperation countering North Korea and China.
Japan's Maritime Self-Defense Force, citing the recent tensions, said it is not inviting South Korea to an international navy review Japan hosts next month.