By Kiyoshi Takenaka
TOKYO (Reuters) - Japan warned on Tuesday of the acute threat posed by North Korea's weapons programs as Pyongyang's continued series of missile and nuclear tests, in defiance of U.N. sanctions, brings technological progress to the reclusive state.
Japan's annual Defence White Paper was released after North Korea fired two intercontinental ballistic missiles (ICBMs) last month that were launched on lofted trajectories and landed off Japan's west coast.
"Since last year, when it forcibly implemented two nuclear tests and more than 20 ballistic missile launches, the security threats have entered a new stage," the Japanese Defence Ministry said in the 563-page document.
"It is conceivable that North Korea's nuclear weapons program has already considerably advanced and it is possible that North Korea has already achieved the miniaturization of nuclear weapons and has acquired nuclear warheads," it said.
North Korea's latest ICBM test showed that Pyongyang may now be able to reach most of the continental United States, two U.S. officials have told Reuters.
The growing threat has prompted Japanese municipalities to hold evacuation drills in case of a possible missile attack, and boosted demand for nuclear shelters.
The white paper said missiles launched on a lofted trajectory were difficult to intercept.
With North Korea pressing ahead with missile tests, a group of ruling party lawmakers led by Itsunori Onodera, who became defense minister on Thursday, urged Prime Minister Shinzo Abe in March to consider acquiring the capability to hit enemy bases.
That, if realized, would be a drastic change in Japan's defense posture. Tokyo has so far avoided taking the controversial and costly step of acquiring bombers or cruise missiles with enough range to strike other countries.
The white paper also expressed concerns over China's expansion in the region, pointing out that the number of Japan's jet scrambles against Chinese aircraft hit a record high in the year to March 2017. The first confirmed advancement of China's aircraft carrier to the Pacific also came in December 2016.
"There is a possibility that their naval activities, as well as air force activities, will pick up pace in the Sea of Japan from now on," the white paper said.
"We need to keep a close eye on the Chinese naval force's activity with strong interest," it said.
Tokyo's ties with Beijing have long been plagued by a territorial dispute over a group of tiny, uninhabited East China Sea islets and the legacy of Japan's wartime aggression.
(Reporting by Kiyoshi Takenaka; Editing by Paul Tait)