United Nations chief Ban Ki-moon is warning the crisis on the Korean peninsula has gone too far, after North Korea reportedly moved a medium-range missile to its east coast and restarted its main nuclear complex.
It's the latest in a round of threats from North Korea against South Korea and the United States that has escalated tensions in the region.
Biwa Kwan reports.
UN Secretary General Ban Ki-moon has appealed to North Korea to change course, saying it has 'gone too far' in its rhetoric.
"Nuclear threats are not a game, it's very serious, and it has... I think they (North Korea) have gone too far in their rhetoric and I'm concerned that if by any misjudgement, by any miscalculations of the situation, if any unwanted crisis happens in the Korean peninsula this will have very serious implications."
The warning came hours after South Korea's Foreign Minister said North Korea had shifted a missile with what he described as considerable range to its east coast.
South Korea's Yonhap news agency reports intelligence analysts believe the east coast missile is a Musudan, which has an estimated range of around 3,000 kilometres or more.
Seoul's Defence Minister Kim Kwan-Jin says while the missile could reach a considerable distance, it could not reach the US mainland.
He has reaffirmed South Korea's readiness to respond to the North's threats.
(through translation) "Our weapons are ready. Regarding North Korea's statement, our military readiness is already high. We are able to manage any possible crisis."
North Korea released a statement yesterday saying it has approved a nuclear strike against the United States.
Responding to North Korea's threat, the US announced it is speeding deployment of an advanced missile defence system to Guam in the next few weeks, two years ahead of schedule.
The land-based missile defence system includes a truck-mounted launcher, tracking radar, interceptor missiles and an integrated fire control system.
The move follows a decision by the US Defence Department earlier this week to reposition two missile defence warships in the Pacific to monitor North Korea.
US Defence Secretary Chuck Hagel says North Korea's recent actions represent a clear and real danger to the United States and its allies South Korea and Japan.
"They have nuclear capacity now. They have missile delivery capacity now. So as they have ratcheted up their bellicose [war-like] rhetoric and some of the actions they have taken over the last few weeks present a real and clear danger and the threat to the interests, certainly of our allies, starting with South Korea and Japan, and also the threats that North Korea has levelled directly at the United States."
US State Department spokeswoman Victoria Nuland has rejected claims that statements from the US government might be fuelling North Korean belligerence.
Ms Nuland says she is focused on achieving a diplomatic solution - if Pyongyang changes its behaviour.
"The DPRK knows what it needs to do, if it wants to make a different choice. If it wants to have support from the international community, economically in terms of supporting its people, it's got to come back into compliance with its international obligations. The president's been clear, the secretary's been clear that if they make a different choice, we will respond. But unfortunately, all we've seen in response to those offers has been more aggressive rhetoric."
The European Union has also weighed into the growing crisis, calling on Pyongyang to stop stoking tensions and re-engage with the international community.
Tensions have soared on the Korean Peninsula since December, when the North test-launched a long-range rocket.
In February, it conducted its third nuclear test and drew fresh international sanctions.
Apart from its threats of nuclear attack, the North has also warned this week it will reopen its Yongbyon reactor - its source of weapons-grade plutonium that was closed in 2007 under an aid-for-disarmament accord.
Meanwhile, Prime Minister Julia Gillard has also emphasised her solidarity with South Korea in a phone hook-up with its president, Park Guen-Hye last night.
Ms Gillard says Australia will continue to call for North Korea to end its aggressive stance and engage in dialogue with South Korea.
Ms Gillard and a delegation of senior ministers are heading to China for six days of talks on economic and security issues.
The visit will include meetings with China's new leadership of President Xi Jinping and Premier Li Keqiang.
Foreign Minister Bob Carr, part of the delegation, told the ABC there will be discussions about North Korea's increasingly provocative behaviour.
"We will raise with China our concern that if the provocative and bellicose behaviour of North Korea continues then it will simply result in rising tensions in North-east Asia and put Japan and South Korea in a position where they will pay more attention to their security."
Meanwhile, North Korea yesterday repeated its threat to completely shut down Kaesong industrial zone, where 123 South Korean firms operate factories, if the South's government continues to mention a possible military action against it.
The jointly operated industrial park 10 kilometres inside North Korea is the last remaining symbol of inter-Korean cooperation.
Its closure would be seen as a clear escalation of tensions beyond all the military rhetoric.
South Korea's Defence Ministry says it had contingency plans, including possible military action, to ensure the safety of its citizens working in the joint industrial zone.
North Korea blocked South Koreans from accessing the complex for the second day running yesterday.
