North Koreans test Iranian nuclear weapon

Awaiting fallout ... the Punggye-ri nuclear test facility in northern North Korea where an 'artificial earthquake' was detected. Photo: GeoEye Satellite Image

NORTH Korea has again defied the world by conducting its third nuclear test, taking the rogue nation 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 Tuesday's 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.

"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 statement said, as reported by the BBC.

The test comes amid acute concern in Seoul, Tokyo and Washington that North Korea is about to cross the technology threshold to possess a credible nuclear warhead and delivery capability.

It also indicates that North Korean leader Kim Jong-un backs the military-first policy of his late father as he solidifies his hold on the country he took charge of 14 months ago.

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 UN backing.

UN Secretary-General Ban Ki-moon condemned the test.

Japanese Prime Minister Shinzo Abe immediately convened his country's security council.

"I 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.

US President Barack Obama said the test was a threat to regional stability that undermined Security Council resolutions and warranted "swift and credible" action by the international community.

"These provocations do not make North Korea more secure," Mr Obama said.

"Far from achieving its stated goal of becoming a strong and prosperous nation, North Korea has instead increasingly isolated and impoverished its people through its ill-advised pursuit of weapons of mass destruction and their means of delivery."

He said Pyongyang's nuclear weapons and ballistic missile programs were a "threat to US national security and to international peace and security" and the US would remain vigilant.

Blast off... South Koreans watch state coverage of North Korea's third nuclear test. Photo: Getty

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.

But there were no signs of a tougher line from China under new president Xi Jinping, with a spokesman on Tuesday night sticking close to previous gentle formulations.

China expressed "resolute opposition" to the test and called on "all sides" to respond ''calmly, through talks".

"To achieve a nuclear-free Korean peninsula, to prevent nuclear expansion, to maintain a peaceful and stable north-east Asia is China’s firm position," the spokesman said.

Last week the chairman of South Korea’s Joint Chiefs of Staff, General Jung Seung-jo, pledged to strike pre-emptively against North Korea if it showed intent to use a nuclear weapon "even at the risk of war".

The possibility of a North Korean nuclear-tipped missile reaching Los Angeles or Darwin is no longer considered fanciful after the North successfully tested a ballistic missile last  December.  

The reference to a ''miniaturised" device in the North Korean statement suggests it has developed a warhead small enough to be fixed to such a missile