Japan has warned that it is possible that North Korea has made serious progress in fitting miniaturised nuclear weapons on missiles – a step which so far experts believed was still years away. Despite the heavy international sanctions and financial clampdown, the North has managed to press on with its nuclear and missile programmes, warned a defence white paper.

Japan's ominous warning comes days after the North fired two intercontinental ballistic missiles (ICBM) within a month. This was the first time Pyongyang launched ICBMs as tensions in the Korean peninsula keep escalating.

The Japanese government said the country faces increasing threats from Pyongyang as the Kim Jong-un regime defiantly refuses to scale down any of its weapons activities. The white paper, issued on Tuesday, 8 August, warned that the North's belligerent actions pose "a new level of threat" to both Japan and the international community.

"It is conceivable that North Korea's nuclear weapons programme has already considerably advanced and it is possible that North Korea has already achieved the miniaturisation of nuclear weapons and has acquired nuclear warheads," said the defence ministry's paper.

"Since last year, when (North Korea) forcibly implemented two nuclear tests and more than 20 ballistic missile launches, the security threats have entered a new stage...The risk that North Korea will deploy nuclear-tipped missiles covering Japanese territory will grow as time passes," added the 563-page report.

The review did not shed any light on whether North Korean scientists have mastered a missile re-entry system – a key stage in the development of a full-fledged nuclear-tipped missile.

There has been a sharp growth in nuclear shelters in recent months in Japan and the government has also conducted evacuation drills in case of a missile attack.

Defence Minister Itsunori Onodera said soon after taking over recently that Tokyo should consider acquiring capabilities to strike North Korean bases in case of a necessity. "We should consider it from the perspective of what Japan can do to beef up the deterrent capability of the Japan-US alliance and protect the lives and property of the Japanese people," Onodera said a day after he took charge of the defence portfolio.

North Korea missile launch and deployment
A view of the test-fire of Pukguksong-2 guided by North Korean leader Kim Jong Un on the spot, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang KCNA via Reuters