The Japanese premier vowed to bolster Japan's defences in the face of the increased threat, but did not provide specific details.
Relations with the North have become more strained in recent months, particularly since the isolationist state conducted its sixth and largest nuclear test in September.
In November, the North said it had successfully tested a new intercontinental ballistic missile that could reach any part of the US mainland.
"It is not an exaggeration to say that the security environment surrounding Japan is at its severest since the Second World War. I will protect the people's lives and peaceful living in any situation," Mr Abe told a New Year news conference.
Japan increased its military budget last month for the sixth year in a row, increasing spending by 1.3 per cent to 5.19 trillion yen (£34bn).
Around 137bn yen was earmarked for improvements to ballistic-missile defences, while 11bn yen was set aside to improve warning systems to help Japan deal with more complex threats, such as multiple missiles fired simultaneously. In March, North Korea launched four missiles simultaneously that landed in the Sea of Japan.
US ambassador to the United Nations, Nikki Haley, said this week the US was hearing reports North Korea might be preparing to fire another missile, and she warned it not to.
“It is absolutely unacceptable that North Korea is trampling the strong desire of Japan and the rest of the international community for peaceful resolutions and continuing with its provocative behaviour,” Mr Abe said.
Mr Abe has said he wants to amend Japan’s pacifist constitution with the aim of loosening constraints on the military, although the public is divided over changes to the charter imposed after Japan’s World War Two defeat.
War-renouncing Article 9 of the constitution, if read literally, bans the existence of standing armed forces, but has long been interpreted to allow a military for exclusively defensive purposes.
Mr Abe said he wanted more debate on the issue.
“I would like this to be a year in which public debate over a constitutional revision will be deepened further,” he said.
Mr Abe’s Liberal Democratic Party-led coalition retained its two-thirds “super majority” in parliament’s lower house in a 22 October election, re-energising his push to revise the constitution.
Reuters contributed to this report
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