user: Teacher:In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Teacher: Now, understand the problem? Solve this instance: North Korea has hinted that it has built a hydrogen bomb to “defend its sovereignty and the dignity of the nation,” a development that, if true, would mark an alarming step in its nuclear capabilities. 
  
 It is the first time that the regime, which has already conducted three atomic tests, has claimed to have built an exponentially more powerful hydrogen bomb. But analysts were doubtful of Kim Jong Un’s latest bellicose claim, saying the young leader appeared primarily concerned with trying to bolster his legitimacy. 
  
 “Do I think they have the capacity to make a hydrogen bomb? I think that’s virtually impossible,” said Daniel Pinkston, an expert on North Korea’s nuclear weapons who is currently at Babes-Bolyai University in Romania. 
  
 Kim, the third-generation leader of North Korea, made the claim while visiting the site of a former munitions factory in central Pyongyang. North Korea has become “a powerful nuclear weapons state ready to detonate self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation,” he said, according to the official Korean Central News Agency. 
  
 [Kim says North Korea ready for any kind of war with U.S.] 
  
 An atomic bomb uses fission to break up the atomic nucleus and release energy, while a hydrogen or thermonuclear bomb uses fusion to add to the nucleus. This leads to an enormous explosion resulting from an uncontrolled, self-sustaining chain reaction. 
  
 The installation that Kim was touring, known as the Phyongchon revolutionary site, was visited several times by founding president Kim Il Sung, the current leader’s grandfather, and by Kim Jong Il, his father. Kim Il Sung reportedly test-fired a submachine gun at the shooting range at the site soon after the division of the Korean Peninsula in 1945. 
  
 The site routinely appears in official documentaries about revolutionary history and on North Korea’s military industrial complex, according to Michael Madden, an expert on North Korea’s leadership. Photos showed Kim Jong Un inspecting rifles inside a building and speaking outside the building, his aides with notebooks at the ready taking down his every word. 
  
 The fact that the statement came not from the National Defense Commission or the politburo, which usually make major pronouncements, but from Kim while he was extolling the achievements of his grandfather and father suggested that he was trying to burnish their legacy and his legitimacy, said Pinkston, a fluent Korean speaker. 
  
 Parsing the Korean version, which was slightly different from the English, he said Kim claimed that the sound of his grandfather’s gun was heard at the site 70 years ago, while today North Korea has become a nuclear state “that can make the boom of a hydrogen or atomic bomb.” It did not necessarily mean that North Korea had developed a bomb, he said. 
  
 “I'm super-skeptical that they’ve been able to make this scientific advancement,” Pinkston said. 
  
 South Korean intelligence specialists also were skeptical and dismissed Kim’s words as rhetoric. “We don’t have any information that North Korea has developed an H-bomb,” Yonhap News Agency quoted an unidentified intelligence official as saying. “We do not believe that North Korea, which has not succeeded in miniaturizing nuclear bombs, has the technology to produce an H-bomb.” 
  
 North Korea's claim to have developed a hydrogen bomb was met with skepticism by the White House on Dec. 10. (Reuters) 
  
 North Korea has a history of making ostentatious claims that cannot be substantiated. In recent months, Pyongyang said it could launch a submarine ballistic missile, had made nuclear warheads small enough to fit on a missile and had restarted its key nuclear facilities at Yongbyon. None of these assertions have been proven. In fact, North Korea appears to have disproved the first claim with a failed missile launch from a submarine last month. 
  
 Satellite images suggest that North Korea might be preparing to conduct a nuclear test again, or at least be ready to test again. 
  
 North Korea has conducted three nuclear tests since 2006, but despite plenty of saber-rattling, it has not detonated a device since the beginning of 2013. Under Kim Jong Un, however, North Korea has repeatedly asserted itself to be a nuclear state and has refused to return to multilateral talks aimed at persuading it to disarm. 
  
 [North Korea builds new tunnel at test site] 
  
 North Korea appears to be building a new tunnel at its nuclear test site, making it more likely that it will test again in the next year, said Jeffrey Lewis, a nonproliferation expert at the Middlebury Institute of International Studies at Monterey, although there are no signs that a test is imminent. 
  
 The International Atomic Energy Agency suggested in September that North Korea appeared to be strengthening its nuclear program, although the agency has not been allowed access to the nuclear facilities. 
  
 Using satellite imagery, the IAEA observed renovation and construction activity at the main Yongbyon plant, which appears to be consistent with the country’s statements that it is further developing its nuclear capabilities, said Yukiya Amano, director general of the IAEA. 
  
 Read more: 
  
 What life looks like inside North Korea 
  
 In a Seoul coffee shop, onetime North Koreans enter the 21st century ||||| North Korean leader Kim Jong-un appeared on Thursday to claim the country has developed a hydrogen bomb, a step up from the less powerful atomic bomb, but outside experts were skeptical. 
  
 Kim made the comments as he toured the Phyongchon Revolutionary Site, which marks the feats of his father Kim Jong-il, who died in 2011 and his grandfather, state founder and eternal president, Kim Il-sung, the official KCNA news agency said. 
  
 The work of Kim Il-Sung "turned the DPRK into a powerful nuclear weapons state ready to detonate a self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation," KCNA quoted Kim Jong-un as saying. DPRK is the acronym for the isolated North's official name, the Democratic People's Republic of Korea. 
  
 A hydrogen bomb, also known as a thermonuclear bomb, uses more advanced technology to produce a significantly more powerful blast than an atomic bomb. 
  
 North Korea conducted underground tests to set off nuclear devices in 2006, 2009 and 2013, for which it has been subject to UN Security Council sanctions banning trade and financing activities that aid its weapons programme. 
  
 An official at South Korea's intelligence agency told Yonhap news agency that there was no evidence that the North had hydrogen bomb capacity, and believed Kim was speaking rhetorically. 
  
 Impoverished North Korea and rich, democratic South Korea remain technically at war after their 1950-53 conflict ended in a truce, not a treaty. The North has threatened to destroy the South and its major ally, the United States, in a sea of flames. 
  
 Despite the underground tests, the North has been seen as short of achieving the capability to put a nuclear warhead on a missile. If the hydrogen bomb claim is true, it would indicate advances in the North's pursuit of nuclear weapons. 
  
 "I think it's unlikely that they have an H-bomb at the moment, but I don't expect them to keep testing basic devices indefinitely, either," said Jeffrey Lewis of the California-based Middlebury Institute of International Studies at Monterey. 
  
 It was possible the North was referring to the technology of boosting the yield of a nuclear device, possibly using fusion fuel, Lewis said. 
  
 North Korea claimed in 2010 that it had successfully developed fusion technology. Assessing progress in the North's nuclear programme is difficult because no one outside a close circle of leaders and experts in Pyongyang knows what advances have been made. 
  
 The North has also boasted to have succeeded in miniaturisation of a nuclear warhead to mount on a ballistic missile, a claim disputed by U.S. and South Korean experts. ||||| (CNN) North Korea has added the hydrogen bomb to its arsenal, state media said Thursday, a development that, if true, would represent a major leap in its nuclear weapons capabilities. 
  
 The announcement came as a top United Nations human rights official told a Security Council meeting that it was "essential" that Pyongyang be referred to the International Criminal Court. 
  
 But outside observers were skeptical, saying that such an advance in nuclear technology seemed unlikely. 
  
 Analysts in recent years have believed that North Korea may have been working toward -- but didn't yet have the capability to produce -- a hydrogen, or thermonuclear, bomb. It can be hundreds of times more powerful than an atomic bomb. 
  
 North Korean leader Kim Jong Un made the claim, according to state media outlet KCNA, while touring a historic weapons industry site in the reclusive communist country. 
  
 North Korea had become "a powerful nuclear weapons state ready to detonate [a] self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation," Kim said, according to the KCNA report. 
  
 The claim is "inextricably linked" to the Security Council meeting, said Jasper Kim, director of the Center for Conflict Management at Seoul's Ewha University. 
  
 "North Korea wants to achieve a stronger bargaining position." 
  
 Observers skeptical 
  
 Experts have responded to Pyongyang's claim with skepticism. 
  
 John Nilsson-Wright, head of the Asia program at Chatham House, said it was "hard to see convincing technical evidence" of Kim's claim, which he believed was the first North Korea had made regarding possessing a hydrogen bomb. 
  
 North Korea had previously used plutonium in nuclear tests, one of the elements used in more "small fry" fission weapons such as atomic bombs, Nilsson-Wright said, and a leap to thermonuclear capability would be surprising. 
  
 "Since the 1980s there is some evidence to suggest a program of developing highly enriched uranium, alongside plutonium, but it's hard to see how they could have made the leap from that to evidence of a working hydrogen bomb," he told CNN. 
  
 Lee Chun-geun, a research fellow at the Science and Technology Policy Institute, shared his doubts. 
  
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 "It's hard to regard North Korea as possessing an H-bomb. I think it seems to be developing it," Lee said, according to a report by South Korea's Yonhap news agency. 
  
 Russian lawmaker Aleksey Pushkov, the head of the foreign affairs committee in Russia's lower legislative house, told state broadcaster Russia 24 that he wasn't sure whether North Korea had a thermonuclear bomb. He said, however, that he believes Kim's regime could be close to having one. 
  
 Difficult to assess 
  
 Hard evidence of North Korea's nuclear progress is difficult to come by, Nilsson-Wright said. 
  
 Kim's regime generally cloaks its efforts in secrecy and occasionally boasts of advances through propaganda outlets, leaving the rest of the world to attempt to connect the dots. 
  
 Nilsson-Wright said such claims were typically made in an "attention-grabbing effort to assert North Korean autonomy and his own political authority" and "enhance its negotiating position with other countries." 
  
 Pyongyang is a "black box", said Ewha's Kim. He added that the regime was well versed in using uncertainty about its true capabilities to generate fear and strengthen its hand in terms of negotiations. 
  
 North Korea's internationally isolated regime is a heavily militarized state with a huge standing army of 1.2 million active soldiers and 7.7 million reservists. 
  
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 But its conventional weaponry is dated, with limited effectiveness, and it has looked to developing its nuclear capabilities to project power internationally. 
  
 The country declared it had nuclear weapons in 2003, and conducted nuclear tests in 2006, 2009 and 2013. 
  
 In May, it said it had the ability to miniaturize nuclear weapons, a development that would allow it to deploy nuclear weapons on missiles. A U.S. National Security Council spokesman responded that the United States did not think the North Koreans had such a capability. 
  
 David Albright, a former U.N. weapons inspector, told CNN earlier this year that Pyongyang could have 10 to 15 atomic weapons at this point, and that it could grow that amount by several weapons per year. 
  
 He said he believed Pyongyang had the capability to miniaturize a warhead for shorter missiles, but not yet for intercontinental ballistic missiles capable of reaching the United States. 
  
 Atomic bomb vs. hydrogen bomb 
  
 The atomic bomb -- the type dropped by the United States over Hiroshima and Nagasaki, Japan, at the end of World War II -- produces a fission reaction, in which a neutron collides with an atom's nucleus, splitting it into two smaller nuclei and releasing energy. Nuclear energy plants use fission to generate electricity. 
  
 A hydrogen bomb produces a fusion reaction -- the energy source of the sun and the stars -- in which colliding nuclei form a new nucleus. Fusion devices produce explosions "orders of magnitude more powerful than atomic bombs," according to the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization. |||||
Student:

assistant: North Korea is known for talking tough when it comes to its nukes, and remarks made by Kim Jong Un Thursday fanned the flames. While touring a museum dedicated to his father and grandfather, the self-proclaimed Supreme Leader suggested that North Korea now has a hydrogen bomb. Grandfather Kim Il Sung "turned [North Korea] into a powerful nuclear weapons state ready to detonate a self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation," said Kim, per the government's state news agency, via the CBC. What's worrisome, if true, is that hydrogen bombs are a much more powerful weapon than atomic bombs, the Washington Post notes. But, as the CBC reports, it's difficult to parse truth from fiction when it comes to North Korea: Previous assertions that remain unverified include claims that it has fired a missile from a sub and that it's able to make mini nukes, per the Post. So not everyone's convinced that Kim's words are much more than rhetorical swagger. "It's hard to regard North Korea as possessing an H-bomb," a research fellow at the Science and Technology Policy Institute notes to CNN. "I think it seems to be developing it." A weapons expert at Romania's Babes-Bolyai University is more straightforward: "I think that's virtually impossible," he tells the Post. (North Korea bragged some more at a recent celebratory anniversary parade.)