North Korea has conducted its second nuclear test since 2006.
The media of the nations involved in the six-party talks on North Korea's nuclear programme have largely condemned the secretive state's second test since 2006, but gave differing views on reasons behind the act and its likely consequences.
One South Korean newspaper pondered whether Seoul now requires its own "deterrent".
Other commentators suggested that Iran - suspected by the US of seeking to develop its own nuclear weapons - would now be watching with interest to see whether the test would be followed up by substantial punishment or merely "a toothless UN Security Council resolution".
EDITORIAL IN CHOSON ILBO
North Korea claims its rationale for having nuclear weapons is to defend itself. South Korea also now requires a deterrent. If the day comes when the republic and the lives of its citizens are threatened, we must take on the problems posed by North Korea's nuclear weapons and missiles by realising that we can no longer accept the limitations of international treaties.
EDITORIAL IN JOONGANG DAILY
North Korea's second nuclear test has changed the world. But we must not panic or get overwhelmed. The government and the people must work together to respond to this new crisis in a calm and rational way.
EDITORIAL IN YOMIURI SHIMBUN
When North Korea pressed ahead with its first nuclear test three years ago, the world entered a dangerous new nuclear age. The country's repeated provocations have further damaged stability and increased tensions in the north-eastern Asian region. We must deal severely with Pyongyang's malicious acts. The international community has to make a level-headed judgment on this problem and deal with it in a co-ordinated manner.
EDITORIAL IN SANKEI SHIMBUN
A North Korean group of more than 50 nuclear and missile engineers, including operatives, visited Iran after North Korea launched a long-range ballistic missile on 5 April, sources close to diplomacy between Japan and the United States revealed yesterday. In Iran, they secretly visited Natanz, where an underground nuclear facility is believed to be located.
EDITORIAL IN CHINA DAILY
China has been firm, consistent in its stance to denuclearise the Korean peninsula. It is opposed to nuclear proliferation because it wants peace and stability to be maintained in north-east Asia and the world beyond.
PROF PANG ZHONGYING IN CHINA DAILY
North Korea's extreme action was a demand for the pace of North Korean-US diplomatic negotiations to be speeded up and a demand for the Obama administration to introduce its new North Korea policy as soon as possible.
WU MIAOFA IN CHINA DAILY
In the eyes of North Korea, nuclear tests and missile launches are the most effective and convenient means to provoke the US. North Korea's nuclear test was in order to demonstrate the dignity of [the] North Korean people to the international community and to show their contempt for UN Security Council sanctions.
EDITORIAL IN SOUTH CHINA MORNING POST
North Korea's nuclear test has again proved how out of step its isolationist regime is with the world in the 21st Century. Pyongyang has to be strongly condemned for its actions. The US has to take the lead in giving North Korea a good reason why it should return to talks.
EDITORIAL IN ORIENTAL DAILY NEWS
Russian leader [Nikita] Khrushchev once asked China not to engage in atomic bombs, if it were not for Mao Zedong's persistence, China would now also be bullied. China's diplomacy in recent years has been running alongside US. It has become a US accomplice and taken [the] road of evil.
YEVGENIY SHESTAKOV IN ROSSIYSKAYA GAZETA
Certain experts believe that the North Korean authorities might at any moment use nuclear weapons against the US, not to mention its nearest neighbours, Japan and South Korea. Such a balance of power fundamentally changes the whole geopolitical situation in the region, giving supporters of the idea of Tokyo and Seoul developing nuclear weapons a clear advantage.
VLADIMIR SKOSYREV IN NEZAVISIMAYA GAZETA
Achievements of the North Korean missile and nuclear scientists seriously affect the balance of power in the Far East. For Washington, and especially for Seoul, the cost of a possible military conflict in the peninsular has risen sharply. It is clear that the DPRK's (Democratic People's Republic of Korea) nuclear rearmament poses a danger to all countries in the region.
IGOR KRYUCHKOV IN GAZETA
In the short term, recent nuclear tests will have the most negative impact on South Korea. The DPRK has demonstrated to its southern neighbour that it will not yield to South Korea, however tough the latter's government is.
ALEKSANDR REUTOV IN KOMMERSANT
The West realises that the current crisis will be a test for the international community with regard to the issue of non-proliferation of nuclear weapons in general. Tehran will take any purely verbal reaction, like a toothless UN Security Council resolution, as evidence of the impotence of the West, first and foremost, and then of the US. It will regard this as a green light to continue developing its nuclear programme.
ANTONOV & ZOZULYA IN IZVESTIYA
The fact that the tests were synchronised [with Iran's missile launch last week] makes one think that they could have been co-ordinated in response to Washington's threats against Pyongyang and Tehran.
DAVID E SANGER IN THE NEW YORK TIMES
Obama must decide how to mix what he called "stronger international pressure" with a new set of diplomatic overtures at a moment when, his aides are acutely aware, Iran and other nations are taking his measure, examining the confrontation with North Korea for hints of how he will handle complex confrontations to come.
GLENN KESSLER IN THE WASHINGTON POST
President Obama came into office saying he wanted to demonstrate that engagement with hostile nations is more effective than antagonism, but North Korea's nuclear test now leaves the young administration with critical choices about its response.
GORDON G. CHANG IN THE WALL STREET JOURNAL
(North Korean leader) Kim Jong-il had one more frightening objective in mind when he set off the nuclear device yesterday. The official Korean Central News Agency said this immediately after the detonation: "The results of the test helped satisfactorily settle the scientific and technological problems arising in further increasing the power of nuclear weapons and steadily developing nuclear technology." This is sales talk. North Korea appears set to go into high gear and merchandise its nuclear arsenal.
EDITORIAL IN KCNA NEWS AGENCY
The nuclear test and the launch of intercontinental ballistic missiles are the options taken by the DPRK to defend itself from the military threat increased by the imperialist forces of aggression and firmly defend the peace on the peninsula and the security of the nation.
BBC Monitoring selects and translates news from radio, television, press, news agencies and the internet from 150 countries in more than 70 languages. It is based in Caversham, UK, and has several bureaux abroad.