- Analysis: Was North Korea's H-bomb test a distraction?
- South doubts claim, saying explosion is too small
Rogue state North Korea claims to have tested its first hydrogen bomb in a move the Turnbull government has condemned as a threat to "peace and security … in our region and beyond".
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North Korea announces nuclear test
North Korea announced on Wednesday that it has tested a nuclear device, after reports of a non-natural earthquake near a previously-used test site.
Foreign Minister Julie Bishop joined much of the world in swiftly slamming the latest provocation by North Korea, vowing to join allies in slapping further sanctions on the already deeply isolated nation.
Experts meanwhile said the test ratcheted up tension across Asia and could help fuel an arms race in the region.
A nuclear blast of some type – the fourth carried out by the regime – was all but confirmed by United States observations of a magnitude 5.1 earthquake in the same area where previous tests have been carried out in the Korean peninsula's north east.
But it is not known whether the explosion was indeed caused by a hydrogen bomb, which is many times more powerful than a traditional atomic device and would represent a significant step forward in North Korea's nuclear program.
The reclusive regime led by 32-year-old Kim Jong-un, whose father and grandfather ruled before him, announced that the "newly developed H-bomb" put North Korea in the "advanced ranks of nuclear weapons states".
Ms Bishop said Canberra would protest directly to Pyongyang and called on the United Nations Security Council to make a "strong response".
"North Korea's ongoing development of nuclear weapons and ballistic missiles, and its proliferation of sensitive technologies, threaten the peace and security of Australia's friends and partners in our region and beyond," she said.
"Today's nuclear test confirms North Korea's status as a rogue state and a continuing threat to international peace and security."
North Korea has previously claimed to have developed miniaturised nuclear warheads that can fit on ballistic missiles. American officials have expressed concern that the latest North Korean missiles could reach the western US.
None of these claims has been confirmed because of the sheer opacity of the hermit state. But it is widely thought the regime has at least a dozen nuclear bombs.
Experts believe the latest test was designed the bolster the regime domestically and also strengthen Pyongyang's hand in international diplomacy, particularly in extracting economic and strategic concessions from the US, South Korea and other key nations.
The test comes ahead of a planned visit by Prime Minister Malcolm Turnbull to Washington later this month where he will meet with President Barack Obama and where security will be a significant issue for discussion.
Professor Jie Chen, an Asia expert at the University of Western Australia, said such demonstrations by North Korea could spur other countries in the region to boost their military capabilities.
"What we're talking about is the broader issue of an arms race … which is already a reality in the region. What worries me is … other countries, mainly Japan, may actually capitalise on North Korea to develop their own nuclear weapon program."
Japan's Prime Minister, Shinzo Abe, branded the nuclear test "a serious threat to the safety of our nation", adding that "we absolutely cannot tolerate this".
The test will also irritate North Korea's only ally, China, which has grown increasingly weary of the hermit nation's persistent provocations.
South Korea's Ambassador to Australia, Bong-hyun Kim, said the test would create "serious tensions in the relationship between North Korea and China, and other neighboring countries".
He said North Korea would continue improving its missile system to threaten other countries.
"However, its effort will face strong resistance from China, South Korea, the US, Japan and others … Neighbouring countries will never recognize North Korea as a nuclear state."
But it is unclear what even the major powers can do. Professor Jie said China's influence over North Korea was often exaggerated.
Michael Raska of the S. Rajaratnam School of International Studies in Singapore said sanctions had proven not to work well.
He said the US needed to change its policy of "strategic patience" which amounted to "waiting for something to change in North Korea".
In the meantime other countries would bolster their military capabilities, including possibly through nuclear shields, he said.
"There will be increasingly more countries introducing more power projection capabilities that would try to mitigate the [North Korean nuclear threat]."
Professor Raska said his greatest concern was what might happen to the existing weapons if there was a coup in North Korea leading to massive instability.