Fortsetzung:
The nuclear test took place under a tunnel beneath a mountain near Mususan-ri, a remote village on North Korea's northeast coast, where the North Korean military launched seven missiles on July 5, according to South Korean lawmakers who attended a closed-door briefing by South Korea's main government spy agency, the National Intelligence Service.
In its official announcement of a nuclear test, North Korea said it marked "a great leap forward in the building of a great, prosperous, powerful socialist nation," and "will contribute to defending the peace and stability on the Korean Peninsula and in the area around it."
Analysts in the region were divided over whether China and South Korea would impose the kind of severe sanctions championed by hawks in Washington and Tokyo - including an immediate stop on oil shipments, trade and aid, as well as the intercepting of North Korean ships - that could unleash instability in North Korea or could trigger more provocations by the North, such as missile tests or armed clashes on the border with the South.
On Monday, South Korea warned North Korea against making such a "mistake" along the inter-Korean border, the world's most heavily armed frontier, because the United States and South Korean militaries are "fully ready to repel any provocation by the North."
Baek Seung Joo, a senior analyst at the Korea Institute for Defense Analyses in Seoul said, "China may agree with the United States that North Korea with nuclear weapons should be under the rule of a leader more rational than Kim Jong Il," whose regime has repeatedly flouted international treaties and has a history of proliferating weapons technology. "The North Korean regime will face the worst yet environment for survival."
Andrei Lankov, a Russian born expert on North Korea who is teaching at Seoul's Kookmin University, said that China, South Korea and Russia would join in sanctions against North Korea, but not for long. Soon enough, they will find excuses, such as famine in North Korea, to resume aid shipments to North Korea and prop up the regime, he said.
"We are going to see a lot of hysterics and tough talk. When all these hysterics are over, things will go back to business as usual, in half a year or in a year or so," Lankov said.
Sanctions at least will have no immediate impact on North Korea, where they are more likely to incite deeper anti-American hatred than anti-Kim Jong Il discontent among the North's 22 million people, who have lived under decades of totalitarian brain-washing, experts say.
Surgical strikes against North Korea's nuclear facilities are highly unlikely because the facilities are hard to detect in a country that keeps most of its key military facilities underground and also because China and South Korea fear such attacks could lead to a full-scale war on the Korean Peninsula, they said.
In South Korea, officials said they believed that an explosion occurred around 10:36 a.m. Monday.
South Korean seismologists, on a round-the-clock alert for signs of a nuclear test in North Korea, detected an underground explosion that triggered a tremor with a magnitude of 3.58 to 3.7, said Yoon Tae Young, spokesman for the presidential Blue House.
That was less than an hour after North Korean officials had called their counterparts in China and warned them that a test was just minutes away.
The Chinese, who have been North Korea's main ally for 60 years but have grown increasingly frustrated by its defiance of Beijing, sent an emergency alert to Washington through the U.S. Embassy in Beijing. Within minutes, President George W. Bush was notified by his national security adviser, Stephen Hadley, that a test was imminent.
South Korea immediately dispatched more guards along its tense border with North Korea, said the office of the South Korean military's Joint Chiefs of Staff.
The suspected test site was located in a region of North Hamgyong Province where American spy satellites have been focused for several years on a variety of suspected underground test sites.
North Korea's decision to conduct the test demonstrated what the world has suspected for years: the country has joined India, Pakistan and Israel as one of the world's "undeclared" nuclear powers. India and Pakistan conducted tests in 1998; Israel has never acknowledged conducting a test or possessing a weapon. But by actually setting off a weapon, if that is proven, the North has chosen to end years of carefully crafted and diplomatically useful ambiguity about its abilities.
The North's decision to set off a nuclear device could profoundly change the politics of Asia.
The explosion occurred only a week after Japan installed a new, more nationalistic prime minister, Shinzo Abe, and just as the country was renewing a debate about whether its ban on possessing nuclear weapons - deeply felt in a country that saw two of its cities incinerated in 1945 - still makes strategic sense.
And it shook the peninsula just as Abe was arriving in South Korea for the first time as prime minister, in an effort to repair a badly strained relationship, having just visited with Chinese leaders in Beijing. It places his untested administration in the midst of one of the region's biggest security crises in years, and one whose outcome will be watched closely in Iran and other states suspected of attempting to follow the path that North Korea has taken.
Now, Tokyo and Washington are expected to put even more pressure on the South Korean government to terminate its "sunshine policy" of trade, tourism and openings to the North - a policy that has been the source of enormous tension between Seoul and Washington since Bush took office.
The explosion was the product of nearly four decades of work by North Korea, one of the world's poorest and most isolated countries. The nation of 23 million people appears constantly fearful that its far richer, more powerful neighbors - and particularly the United States - will try to unseat its leadership. The country's founder, Kim Il Sung, who died in 1994, emerged from the Korean War determined to equal the power of the United States, and acutely aware that General Douglas MacArthur had requested nuclear weapons to use against his country.
But it took decades to put together the technology, and only in the past few years has the North appeared to have made a political decision to speed forward. "I think they just had their military plan to demonstrate that no one could mess with them, and they weren't going to be deterred, not even by the Chinese," a senior American official who deals with the North said late Sunday evening. "In the end, there was just no stopping them."
But the explosion was also the product of more than two decades of diplomatic failure, spread over at least three presidencies. American spy satellites saw the North building a good-size nuclear reactor in the early 1980s, and by the early 1990s the CIA estimated that the country could have one or two nuclear weapons. But a series of diplomatic efforts to "freeze" the nuclear program - including a 1994 accord signed with the Clinton administration - ultimately broke down, amid distrust and recriminations on both sides.
Three years ago, as Bush was sending U.S. troops toward Iraq, the North threw out the few remaining arms inspectors living at their nuclear complex in Yongbyon, and moved 8,000 nuclear fuel rods they had kept under lock and key. Those rods contained enough plutonium, experts said, to produce five or six nuclear weapons, though it is unclear how many the North now stockpiles.
For years, some diplomats assumed that the North was using that ambiguity to trade away its nuclear capability, for recognition, security guarantees, aid and trade with the West. But in the end, the country's reclusive leader, Kim Jong Il, who inherited the mantle of leadership from his father appears to have concluded that the surest way of getting what he seeks is to show that he has the capability to strike back if attacked.
Assessing the nature of that ability is difficult. If the test occurred as the North claimed, it is unclear whether it was an actual bomb or a more primitive device. Some experts cautioned that it could try to fake an explosion, setting off conventional explosives; the only way to know for sure will be if American "sniffer" planes, patrolling the North Korean coast, pick up evidence of nuclear byproducts in the air.
Even then, it is not clear that the North could fabricate that bomb into a weapon that could fit atop its missiles, one of the country's few significant exports.
The North has active missile programs, but it isn't believed to have an atomic bomb design small and light enough to be mounted on a long-range
rocket that could strike targets as far as the United States.
But the big fear about North Korea, American officials have long said, has less to do with its ability to lash out than it does with its proclivity to proliferate. The country has sold its missiles and other weapons to Iran, Syria and Pakistan; at various moments in the six-party talks that have gone on for the past few years, North Korean representatives have threatened to sell nuclear weapons. But in a statement issued last week, announcing that it intended to set off a test, the country said it would not sell its nuclear products.
The fear of proliferation prompted Bush to declare in 2003 that the United States would never "tolerate" a nuclear-armed North Korea. He has never defined what he means by "tolerate," and on Sunday night Tony Snow, Bush's press secretary, said that, assuming the report of the test is accurate, the United States would now go to the United Nations to determine "what our next steps should be in response to this very serious step."
North Korea reports first nuclear test
North Korea said Monday that it had set off its first nuclear test, becoming the eighth country in history, and arguably the most unstable and most dangerous, to proclaim that it has joined the club of nuclear weapons states. The test came just two days after the country was warned by the United Nations Security Council that the action could lead to severe consequences.
In this image taken from North Korean television, a broadcaster reports on the nuclear test.
Nuclear testing is often considered a necessary step to proving a weapon's reliability as well as the most forceful way for a nation to declare its status as a nuclear power.
"Once they do that, it's serious," said Harold Agnew, a former chief of the Los Alamos weapons lab, in New Mexico, which designed most of the nation's nuclear arms. "Otherwise, the North Koreans are just jerking us around."
Senior U.S. officials said they had little reason to doubt the announcement, and warned the test would usher in a new era of confrontation with the isolated and unpredictable country run by President Kim Jong Il, center. North Korea's decision to conduct the test demonstrated what the world has suspected for years: the country has joined India, Pakistan and Israel as one of the world's "undeclared" nuclear powers. By actually setting off a weapon, if that is proven, the North has chosen to end years of carefully crafted and diplomatically useful ambiguity about its abilities.
Networks of seismometers that detect faint trembles in the earth and track distant rumbles are the best way to spot an underground nuclear test. On instruments for detecting earthquakes, such a blast would measure a magnitude of about 4.
A seismic wave measurement being displayed at the Meteorological Agency in Tokyo. Japan is reported to have observed a magnitude 4.9 quake in the northeast region of North Korea where Pyongyang claims to have conducted its test.
Assessing the nature of North Korea's nuclear ability is difficult. It is unclear whether the test was an actual bomb or a more primitive device. Even then, it is not clear that the North could fabricate that bomb into a weapon that could fit atop its missiles.
A South Korean soldier at a check point in Paju near the demilitarized zone on Monday. South Korea's Defense Ministry said the alert level of the military had been raised in response to the test.
The explosion was the product of nearly four decades of work by North Korea, one of the world's poorest and most isolated countries. The nation of 23 million people appears constantly fearful that its far richer, more powerful neighbors - and particularly the United States - will try to unseat its leadership.
The North Korean capital, Pyongyang, on Monday.
"This is a grave threat that shakes stability and peace in Northeast Asia," said a statement from the office of President Roh Moo Hyun of South Korea. "Our government will react sternly under our principle that we can never tolerate the North Korean possession of nuclear weapons." China called the test a "flagrant and brazen" violation of international opinion, and said it "firmly opposes" North Korea's conduct.
South Koreans in Seoul watch a television report about North Korea's nuclear test .
Speaking at a news conference in Seoul, Prime Minister Shinzo Abe of Japan called the test an "unpardonable act." The United States condemned the claim by North Korea that it had conducted a nuclear test as a "provocative act" and called for immediate action by the UN Security Council.
The test occurred just as Abe was arriving in South Korea for the first time as the Japanese leader. It places his untested administration in the midst of one of the region's biggest security crises in years, and one whose outcome will be watched closely in Iran and other states suspected of attempting to follow the path that North Korea has taken.
Abe, front left, reviews an honor guard with Foreign Minister Ban Ki Moon of South Korea, front right, after his arrival in Seoul.
David E. Sanger reported for The New York Times in Washington and Choe Sang-Hun for the International Herald Tribune in Seoul. William J. Broad contributed reporting from New York, and Thom Shanker from Washington.