North Korea Tests a Mightier Nuclear Bomb, Raising Tension

SEOUL, South Korea — North Korea conducted its fifth underground nuclear test on Friday, its government said, despite threats of more sanctions from the United States and the United Nations. The latest test, according to South Korean officials, produced a more powerful explosive yield than the North’s previous detonations, indicating that the country was making progress in its efforts to build a functional nuclear warhead.

The test confirmed the explosive power and other characteristics of a “nuclear warhead that has been standardized to be able to be mounted on” its ballistic missiles, the North’s nuclear weapons institute said in a statement on Friday.

A statement from the South Korean military also said that an artificial tremor, registered as magnitude 5, had originated from Punggye-ri in northeastern North Korea, where the North has conducted its four previous underground nuclear tests.

A senior official at the Defense Ministry later told reporters that it had concluded that a nuclear detonation had caused the tremor.

The ministry estimated the explosive yield was equivalent to 10 kilotons of TNT, the most powerful detonation unleashed in a North Korean nuclear test so far, according to the official, who briefed reporters on the condition of anonymity. The South’s government estimated the North’s last nuclear test, conducted in January, at 4.8 magnitude with an explosive yield of six to nine kilotons. (By comparison, the atomic bomb dropped on Hiroshima in 1945 exploded with 15 kilotons of energy.)


By The New York Times

North Korea’s first nuclear detonation, conducted in 2006, was largely dismissed as a fizzle, registering only as a 3.9 magnitude tremor with about one kiloton of energy. But its nuclear devices have steadily improved, producing bigger explosions with stronger seismic tremors in subsequent tests.

At the same time, the North has launched a series of ballistic missiles with growing ranges that it said were intended to carry nuclear warheads, though doubts persisted that the country had mastered the technology needed to produce a nuclear warhead small and sturdy enough to travel a long distance through Earth’s atmosphere.

On Friday, North Korea reported a major advance in its efforts.

“The standardization of the nuclear warhead will enable the D.P.R.K. to produce at will and as many as it wants a variety of smaller, lighter and diversified nuclear warheads of higher strike power,” it said in a statement on Friday, using the initials of the country’s official name, Democratic People’s Republic of Korea. “This has definitely put on a higher level the D.P.R.K.’s technology of mounting nuclear warheads on ballistic missiles.”

Prime Minister Hwang Kyo-ahn of South Korea called an emergency meeting of top security officials, while his boss, President Park Geun-hye, cut short a visit to Laos, the president’s office said.

The episode unfolded less than a day after President Obama concluded the final Asian tour of his presidency and highlighted the conundrums that the North Korean threat presents to the United States and China, which have often been at odds over how to respond to the bellicose acts of the North’s leader, Kim Jong-un.

In Washington, Ned Price, a National Security Council spokesman, said: “We are aware of seismic activity on the Korean Peninsula in the vicinity of a known North Korean nuclear test site. We are monitoring and continuing to assess the situation in close coordination with our regional partners.”

A meeting to celebrate the 68th anniversary of the founding of the Democratic People’s Republic of Korea was held in the capital, Pyongyang, on Friday. Credit Korean Central News Agency, via Agence France-Presse — Getty Images
The nuclear test sets the stage for a new round of tensions on the divided Korean Peninsula and heightens anxieties elsewhere in Asia and beyond. For the past two decades, Washington has been struggling in vain to stop North Korea’s aggressive, anti-American leaders from arming the country with nuclear weapons.

Although it was long thought that North Korean nuclear and missile tests were intended as muscle flexing for both internal and external consumption, and as a way to exact concessions from the great powers, a growing number of experts and officials say that the North may be committed to assembling a nuclear arsenal that would include smaller weapons that could be mounted on short-range missiles.

Ms. Park said later on Friday that the latest test proved a “fanatical recklessness of the Kim Jong-un regime.”

“The only thing the Kim Jong-un regime will get from this nuclear test will be more intensified sanctions from the international community and deeper isolation,” Ms. Park said. “This kind of provocation will only quicken its eventual self-destruction.”

Prime Minister Shinzo Abe of Japan said that if a test had been conducted, “it simply cannot be justified.” He added that he had instructed government security analysts to collect as much information as possible and share it with the United States, South Korea, China and Russia.

China’s Foreign Ministry said in a statement that Beijing “expresses strong opposition” to the test. “It is the firm stance of China to achieve the denuclearization of the Korean Peninsula, prevent nuclear proliferation, and safeguard the peace and stability of Northeast Asia,” the statement said.

The North Korean leader Kim Jong-un attending what was said to be a drill by artillery units that were testing ballistic rockets. Credit Korean Central News Agency, via Reuters

The foreign minister said China urged North Korea to “stop escalating” its actions and to abide by United Nations resolutions that forbid nuclear tests.

Though Beijing’s relations have been strained over Pyongyang’s growing nuclear ambitions, China’s leader, Xi Jinping, has refrained from severely punishing Mr. Kim.

The Obama administration has pointed to North Korea as one of the issues where China and the United States could work together, and praised China for supporting United Nations sanctions imposed this year against North Korea.

But reports from the border region with North Korea show that Chinese trade continues, and Washington and Beijing increasingly differ on how to deal with the North’s nuclear program.

When South Korea agreed in July to the American request to deploy an antimissile system, known as the Terminal High Altitude Area Defense system, as protection against North Korea’s nuclear weapons, China strongly protested and even suggested that the deployment was as provocative as the North Korean tests.

At the meeting between Mr. Obama and Mr. Xi in Hangzhou, China, last week, the Chinese leader reiterated his opposition to the deployment of the Thaad system, asking the United States to respect China’s strategic interests.

One of China’s biggest fears is a collapse of North Korea that would result in a unified Korean Peninsula under an American defense treaty. For that reason, Chinese analysts say, China has tolerated Mr. Kim’s advances in nuclear weapons.

North Korea last tested a nuclear device on Jan. 6. In April, Ms. Park warned that the North might be preparing for another underground nuclear test in defiance of United Nations sanctions.

Suspicions that Pyongyang had set off another nuclear device arose quickly on Friday after a tremor was reported near where previous tests have been carried out; actual earthquakes are rare on the Korean Peninsula.

The North Korean statement was read by Ri Chun-hee, 73, on Central Television, the state-run broadcaster. Ms. Ri, known to the outside world for her soaring, bombastic voice, has been assigned to read all the North’s most important announcements, including the death of Mr. Kim’s father, Kim Jong-il, in 2011. South Korean monitors brace themselves whenever Ms. Ri, typically clad in a pink traditional Korean dress, appears on TV and opens what they call her “cannon mouth.”

Friday will be the 68th anniversary of the founding of the North Korean government. The country often celebrates its major holidays with displays of military might. Last week, it fired three ballistic missiles into the sea between the North and Japan, prompting the United Nations Security Council to urge the North to stop provocations or face more sanctions.

In March, the North Korean state news media reported that Mr. Kim had ordered that a “nuclear warhead explosion test” be conducted soon, as well as tests of ballistic missiles capable of delivering nuclear warheads. North Korea has since launched a series of ballistic missiles, including one fired from a submarine last month.

After the North’s nuclear test in January, and a long-range rocket launch weeks later, the United Nations Security Council imposed additional sanctions on the country, with the support of China. But the North has continued to flaunt its nuclear ambitions with a series of tests and claims about what it says are its growing technological capabilities.

Since inheriting power from his father, Kim Jong-il, in late 2011, Kim Jong-un has called for accelerating the North’s pursuit of long-range missiles and nuclear weapons in defiance of international pressure. Three of the North’s five nuclear tests have been conducted under his rule.

In recent months, North Korea has indicated that it is now capable of building a warhead compact and sophisticated enough to mount on an intercontinental ballistic missile. But such claims have been difficult to verify.

North Korea has never flight-tested a long-range missile, and officials and analysts in the region generally doubt that it has built a reliable ICBM. But the leaders of two government-run research institutes in Seoul have recently said that they believed North Korea was now able to mount a nuclear warhead on a short-range Scud or medium-range Rodong missile, if not on an ICBM.

Pyongyang said its Jan. 6 nuclear test was of a hydrogen bomb, which would have been a major escalation in its capacity for destruction.

Yet analysts were skeptical of the claim, saying that such a weapon would have generated a much bigger seismic wave. Some experts said the North might have tried to bolster the yield of a more basic device by using tritium, a radioactive form of hydrogen.