SEOUL/WASHINGTON (Reuters) - North Korea said on Monday it successfully tested what it called an intermediate-range ballistic missile, which met all technical requirements and could now be mass-produced, although U.S. officials and experts questioned the extent of its progress. 
 
 The United States, which has condemned repeated North Korean missile launches, said Sunday’s launch of what North Korea dubbed the Pukguksong-2 was of a “medium-range” missile, and U.S.-based experts doubted the reliability of the relatively new solid-fuel type after so few tests. 
 
 U.S. officials, who spoke on condition of anonymity, said the test did not demonstrate a new capability, or one that could threaten the United States directly. But the test was North Korea’s second in a week and South Korea’s new liberal government said it dashed its hopes for peace. 
 
 U.S. officials have been far less sanguine about the test of a long-range KN-17, or Hwasong-12, missile just over a week ago, which U.S. officials believe survived re-entry to some degree. 
 
 North Korea said that launch tested the capability to carry a “large-size heavy nuclear warhead” and put the U.S. mainland within “sighting range.” 
 
 Western experts say the Hwasong-12 test did appear to have advanced North Korea’s aim of developing an intercontinental ballistic missile capable of reaching the U.S. mainland, even if it is still some way off from achieving that capability. 
 
 The U.N. Security Council is due to meet on Tuesday behind closed doors to discuss Sunday’s test, which defies Security Council resolutions and sanctions. The meeting was called at the request of the United States, Japan and South Korea. 
 
 Washington has been trying to persuade China to agree to new sanctions on North Korea, which has conducted dozens of missile firings and tested two nuclear bombs since the start of last year. 
 
 U.S. President Donald Trump has warned that a “major, major conflict” with North Korea is possible over its weapons programs, although U.S. officials say tougher sanctions, not military force, are the preferred option. 
 
 North Korea’s state news agency, KCNA, said the latest missile test was supervised by leader Kim Jong Un and verified the reliability of Pukguksong-2’s solid-fuel engine, stage separation and late-stage guidance for a nuclear warhead. It said data was recorded by a device mounted on the warhead. 
 
 ‘PRIDE’ 
 
 “Saying with pride that the missile’s rate of hits is very accurate and Pukguksong-2 is a successful strategic weapon, he (Kim) approved the deployment of this weapon system for action,” KCNA said. 
 
 “Now that its tactical and technical data met the requirements of the Party, this type of missile should be rapidly mass-produced in a serial way ..., he said.” 
 
 KCNA said Kim was able to view the Earth from a camera mounted on the missile. “Supreme leader Kim Jong Un said it feels grand to look at the Earth from the rocket we launched and the entire world looks so beautiful,” KCNA said. 
 
 South Korea’s military said the missile flew about 500 km (310 miles), reaching an altitude of 560 km (350 miles). 
 
 It said the test would have provided more “meaningful data” for North Korea’s missile program, but further analysis was necessary to determine whether Pyongyang had mastered the technology needed to stop the warhead burning up on re-entering the Earth’s atmosphere. 
 
 U.S.-based experts said the Pukguksong-2 would have a maximum range of about 1,500 km (930 miles) and questioned North Korea’s assertion that the reliability of the solid-fuel missile had been proven, given limited testing. 
 
 “Entering mass production this early in the development phase is risky, but perhaps a risk North Korea feels comfortable managing,” said Michael Elleman of the International Institute for Strategic Studies. 
 
 Jeffrey Lewis, of the California-based Middlebury Institute of International Studies, said North Korea would probably continue to test the missile after deployment, fixing flaws as they emerged. 
 
 The use of solid fuel presents advantages for weapons because it is more stable and can be transported easily allowing for a launch at very short notice from mobile launchers. 
 
 Developing longer-range solid fuel missiles, however, was highly complicated and would “take time, lots of it,” Elleman said. 
 
 John Schilling, a missile expert contributing to Washington’s 38 North think tank, estimated it would take until at least 2020 for North Korea to be able to develop an ICBM capable of reaching the U.S. mainland and until 2025 for one powered by solid fuel. 
 
 North Korea’s current missiles already pose a threat to South Korea and Japan and the tens of thousands of U.S. troops based in both countries. 
 
 Daniel Russel, Washington’s former top diplomat for Asia, said Pyongyang’s aim appeared to be to convince the United States and the rest of the world of the need to accept North Korea as a nuclear-armed state. 
 
 “The intended message to the United States is that your pressure campaign won’t work and we’ll see your sanctions and raise you yet another advance in our ballistic missile program,” Russel, now diplomat in residence at the Asia Society Policy Institute, told Reuters. 
 
 The scene of the intermediate-range ballistic missile Pukguksong-2's launch test. KCNA/via REUTERS 
 
 On Sunday U.S. Secretary of State Rex Tillerson termed North Korea’s missile testing “disappointing, disturbing” and said economic and diplomatic pressure would continue. 
 
 Japan’s chief Cabinet secretary, Yoshihide Suga, said on Monday it was important to cut North Korea’s foreign currency earnings and to block shipments and technology transfers that aid North Korea’s nuclear missile development. 
 
 China repeated its call for all parties to exercise restraint and not let tension mount further. ||||| Experts cast doubt on claim, saying evidence points to test involving uranium or plutonium device, while UN security council will discuss possible sanctions 
 
 North Korea has conducted its fourth nuclear test, the country’s state media has announced, in a move that could take it a step closer to developing nuclear warheads capable of striking the US mainland. 
 
 
 
 Some experts, though, said initial evidence was pointing towards a test involving a uranium or plutonium device and not, as Pyongyang has claimed, a far more powerful hydrogen bomb. 
 
 North Korea to make 'major announcement' following artificial earthquake near nuclear test site – live Read more 
 
 An announcement on North Korean television said the country had successfully tested a “miniaturised hydrogen bomb” underground on Wednesday morning, describing it as an “act of self-defence” against the US. North Korean claims about the size and type of bomb have not been independently verified. 
 
 If the claims are true, it would be the first time the North has successfully tested a hydrogen bomb and could also enable the secretive state to launch long-range nuclear missiles. 
 
 “If it’s true, it means they’ve made something smaller scale, capable of being put onto a missile, said John Carlson, the former head of the Australian Safeguards and Non-Proliferation Office. “I think we can assume the previous tests they’ve carried out have been devices too large to fit onto a missile.” 
 
 South Korea’s spy agency believes the seismic wave reported was more likely caused by an atomic bomb, Lee Cheol Woo, a South Korean politician, said. 
 
 Yang Uk, a senior research fellow at the Korea Defence and Security Forum, said: “Given the scale it is hard to believe this is a real hydrogen bomb. They could have tested some middle stage kind (of device) between an A-bomb and H-bomb, but unless they come up with any clear evidence, it is difficult to trust their claim.” 
 
 The North Korean state television broadcast said the test was a “complete success” which propelled the country into the “rank of advanced nuclear states”. It had been overseen by the country’s leader, Kim Jong-un and conducted ahead of his 33rd birthday this Friday. 
 
 
 
 “[North Korea’s] fate must not be protected by any forces, only by [North Korea] itself,” the broadcast said. North Korea would not abandon its nuclear weapons program as long as the US maintained what it called “its stance of aggression”. 
 
 “The US has gathered forces hostile to DPRK [Democratic People’s Republic of Korea] and raised a slanderous human rights issue to hinder DPRK’s improvement,” it said. 
 
 “It is just to have H-bomb as self-defence against the US having numerous and humongous nuclear weapons. The DPRK’s fate must not be protected by any forces but DPRK itself.” 
 
 The United Nations security council was planning to meet on Wednesday morning in New York to discuss North Korea’s nuclear test, council diplomats said. 
 
 The White House said it could not confirm North Korea’s claims, but added the United States would respond appropriately to provocations and defend its allies. The EU said the test was a “grave violation” of UN resolutions. 
 
 Phillip Hammond, the British foreign secretary, said on a visit to Beijing: “I think I can say that Britain and China are pretty much completely aligned on North Korean nuclear. We both strongly oppose the acquisition or testing of nuclear weapons by North Korea and we both want to see a resumption of the six party talks. 
 
 “So far as I think any of us can tell, there is no reason to doubt what the North Koreans are claiming – that they have carried out a test detonation of an H bomb. It is clearly very bad news for the non-proliferation agenda generally and for security in the region specifically.” 
 
 South Korean president Park Geun-hye said the country would take decisive measures against any additional provocations by North Korea and work with the international community to make sure the country pays the price for its latest nuclear test. 
 
 Park said the latest test could change the fundamental nature of the situation over North Korea’s nuclear programme. 
 
 Prime minister Shinzo Abe said Japan would make a firm response to North Korea’s challenge against nuclear non-proliferation, calling its test a threat to Japan’s security. 
 
 
 
 The test is bound to ratchet up tensions between the isolated country and its neighbours as well as Washington. China’s foreign ministry said that Beijing did not have advance knowledge of the test and added that it firmly opposes Pyongyang’s action. 
 
 
 
 North Korea conducted nuclear tests in 2006, 2009 and 2013, drawing condemnation and rounds of UN sanctions banning trade and financing activities that aid its weapons program. 
 
 
 
 A successful fourth test could deepen North Korea’s international isolation if the UN security council decided to respond with more sanctions. Pyongyang is thought to have developed several crude nuclear weapons. 
 
 Timeline: North Korea’s nuclear weapons development Read more 
 
 Since becoming North Korean leader in late 2011, Kim Jong-un has stepped up condemnation of joint US-South Korean military drills he believes are preparation for an invasion. 
 
 
 
 In early 2013, Kim responded to UN sanctions imposed after North Korea’s third nuclear test by unleashing a barrage of threats aimed at South Korea, the US and Japan. 
 
 Kim appears to have caught the world off-guard yet again. He did not mention his country’s pursuit of a nuclear deterrent in his New Year’s address, an omission some analysts say was designed to improve the prospects of a summit with the Chinese leader, Xi Jinping. 
 
 Last month Washington dismissed Kim’s claims that his country had developed a hydrogen bomb – a development that, if true, would mark significant progress in North Korea’s nuclear capability. Hydrogen bombs are capable of producing a far more powerful blast than basic atom bombs. 
 
 An intensity shake map released by the US Geological Survey on 5 January shows the location where a preliminary 5.1 magnitude earthquake struck in North Korea. Photograph: US Geological Survey/EPA 
 
 John Carlson said the veracity of North Korea’s claim would be difficult to determine “until we can analyse any gases emitted, and it could take several days for those to show up, if it all”. 
 
 He said it would be a “major challenge” for the North Korean regime to develop a thermonuclear weapon, particularly a miniaturised version, which required even greater expertise. 
 
 “Their claim would be far more convincing if it was a larger size,” he said. 
 
 Carlson, who headed Australia’s safeguards office for more than two decades, said it was possible Pyongyang had actually produced a lower-yield “boosted explosion”, in which the hydrogen isotope tritium undergoes partial fusion, allowing them to describe the device as a hydrogen bomb. 
 
 “I think it’s feasible that they’ve done that and they’re claiming that they’ve done more,” he said. 
 
 Speculation that the regime in Pyongyang had conducted a surprise nuclear test on Wednesday rose after seismologists from South Korea, China and other countries said they had detected a “manmade” earthquake in the country that could have been caused by an explosion. 
 
 
 
 South Korean meteorological officials said the epicentre of the quake was 49km (30 miles) from the Punggye-ri site in North Hamgyong province, where North Korea has conducted nuclear tests in the past. 
 
 How to stop worrying and embrace a nuclear North Korea Read more 
 
 Yonhap news agency in South Korea said North Korea had not given notice of the test, which was carried out at 10am local time (1am GMT), to the US or its traditional ally China. 
 
 Wednesday’s tremor was a “suspected explosion”, the China earthquake network centre said on its website. It gave the magnitude as 4.9. 
 
 The US Geological Service said it had detected a 5.1 magnitude quake, and the European Mediterranean seismological centre said it had also detected unusual seismic activity in North Korea. 
 
 “We suspect a manmade earthquake and are analysing the scale and epicentre of the quake with the geoscience and mineral resource institute of South Korea,” a Korea meteorological administration official said in the South Korean capital, Seoul.
– Having tried out mid-range ballistic missiles in recent weeks, North Korea said today it may conduct a "new form" of nuclear test, the New York Times reports. Pyongyang officials didn't clarify, but the US and its allies have long thought North Korea wants to build small, sophisticated nuclear devices that can ride piggyback on its new missiles. A spokesman for South Korea's foreign ministry said North Korea "will have to pay a price" if it ignores international concerns and carries out the test. For its part, North Korea accused the UN of "turning a blind eye" to "US madcap nuclear war exercises" while denouncing North Korea's, Reuters reports. North Korea also said it wants the ability to hit medium- and long-range targets "with a variety of striking power." Tensions between North and South Korea eased last month, when elderly people separated by the Korean War were allowed short reunions, but the North has since returned to harsh rhetoric—and a paper by a nuclear expert cited the "disquieting possibility" that North Korea is building a network of tunnels to carry out regular nuclear tests with highly enriched uranium.