BEIJING: North Korea has once again defied the world to conduct its third nuclear test, taking the hermit kingdom a step closer to a credible nuclear weapon that could theoretically strike the United States or Australia.
A statement from the state-run KCNA news agency confirmed the test, hours after a seismic shock registering about 5 was recorded emanating from the northern region of North Korea, where the two previous nuclear tests were conducted in 2006 and 2009.
North Korea quake a nuclear test?
A 5.1-magnitude earthquake is detected in the same location as North Korea's Punggye-ri nuclear test site.
''It was confirmed that the nuclear test that was carried out at a high level in a safe and perfect manner using a miniaturised and lighter nuclear device with greater explosive force than previously did not pose any negative impact on the surrounding ecological environment,'' the BBC quoted the statement as saying.
The US Geological Survey said the epicentre of the quake was a kilometre underground and the blast took place at 11.57am Korean time (1.57pm AEDT).
The test comes amid acute concern in Seoul, Tokyo and Washington that North Korea is about to cross the technology threshold to possessing a credible nuclear warhead and delivery capability.
The UN security council was reportedly convening an emergency meeting in New York but potential target nations are likely to seek tougher measures with or without United Nations backing.
The Japanese prime minister, Shinzo Abe, immediately convened his country’s security council.
‘'' have ordered that we consider every possible way to address this issue, including our own sanctions, while co-operating with other countries,'' he said after the meeting.
South Korea, Japan and the US are searching for fresh points of leverage that might convince North Korea’s sole ally, China, to intervene and obstruct the nuclear weapons program.
Last week the chairman of South Korea’s Joint Chiefs of Staff, General Jung Seung-jo, pledged to pre-emptively strike against North Korea if it showed intent to use a nuclear weapon ''even at the risk of war''.
Such a strike would hit a sensitive nerve in Chinese security circles, where North Korea is considered a strategically crucial buffer state.
But Chinese regional security analysts seem convinced that Beijing could not force Pyongyang to give up its nuclear weapons program even if it tried.
The possibility of a North Korean nuclear-tipped missile reaching as far as Los Angeles or Darwin is no longer considered fanciful after the North successfully tested a ballistic missile in December.
The reference to a ''miniaturised'' device in the North Korean statement suggests it may have developed a warhead small enough to be fixed to such a missile.
Nuclear jolt to defence spend
In the wake of North Korea's third confirmed nuclear test, chief government whip Joel Fitzgibbon and Liberal MP Josh Frydenberg discuss the importance of minimising defence budget cuts.
The latest North Korean nuclear test places its only ally, China, in a tighter bind, as the country is now surrounded on all sides by nuclear weapons states.