North Korea's state media said leader Kim Jong Un inspected the loading of a hydrogen bomb into a new intercontinental ballistic missile. Credit:AP "If that's the case, we are seeing North Korea enter into a super league of the thermonuclear club - there are only a handful of nations that operate at this level. "This is also a real slap in the face to President Trump in the US, who has spoken about fire and fury. Here Kim is, basically going back to President Trump and saying 'Go on, I dare you.' " The test "presents a really significant threat not only to South Korea but to the world," Professor Blaxland said. Prime Minister Malcolm Turnbull said Australia "utterly condemns North Korea's flagrant defiance of United Nations Security Council resolutions which ban nuclear weapons development and testing by Kim Jong-un's regime".

"North Korea's reckless conduct poses a grave danger to global peace and security," he said on Sunday. "We call for the UN Security Council to urgently consider further strong measures that would place pressure on North Korea to change course, and for all nations, especially the Permanent Five UNSC members, to apply the maximum possible pressure to this dangerous pariah regime." Australia is doing its part to exert pressure on North Korea through full implementation of UNSC and autonomous sanctions. "We have repeatedly said we are committed to the path of diplomatic and economic pressure to resolve this crisis," Mr Turnbull said. "We will continue to work with our ally and partners to change North Korea's behaviour and deter it from threatening the region and the world with illegal weapons.

"We welcome China's intent to implement sanctions and urge it to use its substantial economic and political leverage to rein in North Korea's actions." Japan and South Korea concluded on Sunday afternoon that the tremor had been caused by a nuclear test. China's Earthquake Administration said it had detected a 6.3 magnitude earthquake in North Korea that was a "suspected explosion", conducted at zero depth. It said it detected a second quake in North Korea of magnitude 4.6, which it termed as a "collapse". It said the second quake, measured at a depth of zero kilometres, came eight minutes after the first quake. The co-ordinates of the two quakes were almost identical.

Residents in the Chinese city of Yanji, on the border with North Korea, said they felt a tremor that lasted roughly 10 seconds, followed by an aftershock. South Korea convened a national security council meeting to discuss the crisis. Hours before the test, North Korea's official mouthpiece, the Korean Central News Agency, said North Korean scientists had built an advanced hydrogen bomb that could be mounted onto an intercontinental ballistic missile and had an explosive power that was adjustable up to "hundreds" of kilotons. Later on Sunday, it said a test of the bomb had taken place to "examine and confirm the accuracy and credibility" of the country's technology. The nuclear test was the sixth and largest conducted by North Korea.

In July, North Korea tested two intercontinental ballistic missiles, which experts said could reach parts of the US. In response, the United Nations Security Council voted unanimously to impose increased sanctions on the regime worth more than $US1 billion ($1.25 billion). Last week, North Korea fired a test missile that flew over Japan, prompting the US and its allies to send fighter jets and bombers over the Korean Peninsula in a so-called "show of force" operation. In response to the latest suspected test, Australian Labor deputy leader Tanya Plibersek said it was vital the international community continued to assert pressure for peace and a de-escalation of the situation. "The greatest threat to peace and stability in our region at the moment is the conflict that is emerging on the Korean Peninsula.

"Right across our region, government would be watching North Korean actions with a great deal of concern and trepidation. We know that really the only friend North Korea has is China ... We do ask the government of China to continue to make extra efforts to reduce the likelihood of a very dangerous situation emerging." In August, Trump threatened to unleash "fire and fury" against North Korea if Kim continued issuing threats against the US. "North Korea best not make any more threats to the United States," Trump told reporters at his golf club in New Jersey during a working holiday. "They will be met with fire and fury like the world has never seen. "He has been very threatening beyond a normal state, and as I said, they will be met with fire and fury, and frankly power the likes of which this world has never seen before."

The comments, which were later reported to have been made off the cuff, stoked fears of the possibility of nuclear war, not least because they appeared to change US policy on North Korea, which has been only to respond to force with force. Trump's rhetoric also marked a departure from the firm measured language on the regime used by his predecessors. Senator John McCain, the chairman of the powerful Armed Services Committee, said he feared the rhetoric would only increase tension. "All it's going to do is bring us closer to some kind of serious confrontation." Undeterred by the comments, North Korea responded by saying it would create "an enveloping fire" around Guam, the western Pacific island which is home to a major US Air Force base.

Various US attempts to address the North Korean situation have all ended in failure. At the start of his administration, Trump declared the policy of "strategic patience" - a reference to Barack Obama's approach - was over. So far, though, the new administration's harder line has met with no more success. In an unguarded interview he gave shortly before he resigned as Trump's chief strategist, Steve Bannon said that there was "no military solution" to nuclear threats posed by North Korea. "Until somebody solves the part of the equation that shows me that 10 million people in Seoul don't die in the first 30 minutes from conventional weapons, I don't know what you're talking about; there's no military solution here, they got us." Experts and officials have said North Korea could conduct its sixth nuclear test at any time, and that the reclusive country has maintained a readiness at its nuclear test site to conduct another detonation test at any time.

Russian President Vladimir Putin has warned that the stand-off between North Korea and the United States is close to spilling into a large-scale conflict, and said it was a mistake to try to pressure Pyongyang into halting its nuclear missile program. After the missile launch over Japan, Trump dismissed the idea of negotiating with Kim's regime but his defence chief said the US hadn't exhausted its diplomatic options. After suggesting that North Korea's leader "is starting to respect us", Trump on Wednesday returned to his tougher line. "The US has been talking to North Korea, and paying them extortion money, for 25 years. Talking is not the answer!" he said in a Twitter post. South Korea, the US and Japan are pressing China to impose stronger economic measures to stop Kim's nuclear ambitions.

The United Nations Security Council has unanimously voted to tighten sanctions that targeted about a third of North Korea's $US3 billion in exports. The UN has banned North Korea from developing nuclear weapons and imposed sanctions after past tests. Kim's regime has said it won't give up its nuclear weapons and missile program until the US drops its "hostile" policies such as joint military drills with South Korea that ended last week. Loading North Korea and South Korea, along with its allies including the United States and Australia, have technically been at war since Korean War hostilities ended with an armistace in 1953.

with agencies