(CNN) China is further fortifying its northern border region, which includes North Korea, amid continued tensions on the Korean Peninsula and concerns over potential US military action against Pyongyang. 
 
 The North Korean-Chinese border stretches 880 miles (1,415 kilometers) across China's Liaoning province, an industrial and mining heartland prone to heavy smog and painfully cold winters. 
 
 In more hospitable months, the border city of Dandong plays host to hundreds of tourists coming to gawp at North Korea -- from boats on the Yalu River which separates the two countries, or through binoculars on a section of the Great Wall overlooking the international boundary. 
 
 Can China help the US deal with North Korea? 
 
 Can China help the US deal with North Korea? 02:18 
 
 Can China help the US deal with North Korea? 
 
 Below the tourists, trucks carrying Chinese goods rumble into North Korea as a small number of shoppers and traders head in the opposite direction. 
 
 But recent reports published on Chinese military and government websites, first highlighted by the Wall Street Journal , show Beijing is moving to reinforce the border as tensions on the Korean Peninsula rise and some in the US call for regime change in Pyongyang. 
 
 Chinese vendors sell North Korea and China flags on the boardwalk next to the Yalu river in the border city of Dandong in China's Liaoning province. 
 
 High security 
 
 According to a report published last month on the official website of the People's Liberation Army (PLA), a "newly formed border defense brigade" is conducting patrols to gather intelligence, assess the situation and more accurately map out the border region -- which includes North Korea, Russia and Mongolia. 
 
 Another report said the "whole area" has newly been placed under "24-hour video surveillance" including drones, patrol cars and high-tech cameras. 
 
 The North Korea border region is a highly strategic one for China, and has seen conflict during World War II and the Korean War, but one of Beijing's chief concerns is not military forces pouring across the border, but refugees. 
 
 "A mass movement of North Korean civilians across the border into China is a major concern, particularly given the dense population centers not far from the border, and the economic importance of Northeast China," according to a recent report by the US-based Jamestown Foundation. 
 
 While North Korea has proved remarkably capable of shrugging off economic sanctions, the country has suffered major famines and widespread food insecurity in the past, analysts say a conflict on the peninsula would likely result in hundreds of thousands, if not millions, of civilians heading north into China, the specter of which is a "huge worry for Beijing" according to the Council on Foreign Relations. 
 
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 Just as the Syrian refugee crisis has strained the resources of neighboring countries and caused widespread political strife in Europe, many in China are concerned by the hit the country's economy and security could take from even a small conflict on the Korean Peninsula. 
 
 "The stakes are huge," retired US Adm. Mike Mullen said last year . "Instability generated on the peninsula could cascade into China, making China's challenge of providing for its own people that much more difficult." 
 
 In March, retired PLA Major General Wang Haiyun said it was "necessary to prepare military action as soon as possible for a potential war" on the peninsula. 
 
 "Once war breaks out, we should also consider setting up an international refugee camp in North Korean territory to prevent the influx of North Korean refugees," said Wang in an op-ed in the state-owned Global Times. 
 
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 Warnings of war 
 
 Tensions between Pyongyang and Washington have continued to rise amid recent claims by North Korea that it had tested a nuclear-capable intercontinental ballistic missile (ICBM) 
 
 A US defense official told CNN this week North Korea appeared to be preparing for another test 
 
 The Donald Trump administration has sought to bring pressure on China to take action to contain its ally, but despite repeated condemnations by Beijing of North Korea's weapons testing, little progress appears to have been made. 
 
 Beijing has also criticized the US and South Korea for their rhetoric on the issue and encouraged all parties to return to the negotiating table. 
 
 However, such an invitation from Seoul to Pyongyang to resume talks went unanswered this month 
 
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 The situation has led to frustration on all sides, with Trump's CIA director Mike Pompeo last week appearing to indicate support for regime change in Pyongyang 
 
 Tong Zhao, an analyst at the Carnegie Tsinghua Center for Global Policy, said that "given the growing tensions and risks of military conflicts over the peninsula, I am sure China has been enhancing its military contingency plans." 
 
 On Monday, a Chinese Ministry of Foreign Affairs (MOFA) spokesman said "military means should not be an option to solve the Korean Peninsula issue." A Defense Ministry spokesman declined to comment Monday on China's war contingency plans. 
 
 Speaking Tuesday, MOFA spokesman Lu Kang said the country's military "has maintained normal combat readiness and training status along the Chinese-North Korean border." 
 
 Earlier this year, the Chinese state-run tabloid Global Times warned "if the North Korean nuclear issue boils over, a war on the peninsula is unavoidable." ||||| Experts say leaked contingency plans, which include the detention of leaders and establishment of refugee camps, may be valid but do not suggest that the alliance is weakening 
 
 China has angrily dismissed reports that it has drawn up contingency plans for the collapse of the regime in North Korea, including measures to contain an influx of refugees and prevent unrest from spilling over the countries’ porous border. 
 
 The People’s Liberation Army (PLA) devised the measures last summer, according to Kyodo news agency, which reported the leaked documents this week. But experts said they did not signal that Beijing was losing faith in North Korean leader Kim Jong-un. 
 
 The documents, which Kyodo said it had obtained from unnamed Chinese military sources, include plans to detain North Korean leaders and set up refugee camps along the border, each able to accommodate up to 1,500 people. 
 
 In Beijing, a foreign ministry spokesperson said reports of the alleged contingency plans were “groundless”, according to Xinhua. 
 
 “The report made wild guesses, and was groundless and with ulterior motives,” the spokesperson said, adding that China’s stance was “clear”. 
 
 “We hope the Korean peninsula maintains stability, and hope [North Korea] achieves economic development and people’s happiness,” the spokesperson said. 
 
 John Delury, a North Korea analyst at Yonsei University in Seoul, said there was no evidence to suggest that Chinese military officials had leaked the story to signal Beijing’s annoyance with Pyongyang or because it thought there was a credible threat to the regime. 
 
 Delury said: “I wouldn’t believe China’s denials – of course it’s going to say that. China is never going to make something like this public. The PLA is doing what militaries do – they draw up contingencies. But we shouldn’t draw too many conclusions from this.” 
 
 The PLA documents were reportedly drawn up in the summer of 2013, several months after North Korea drew widespread condemnation, including from China, for conducting its third nuclear test. 
 
 They call for better monitoring of China’s 1,416km border with North Korea and the construction of camps to house an expected influx of refugees. 
 
 The plans reportedly do not mention North Korea by name, but refer to “our country’s north-east neighbour” or “the country next door with the hereditary system”, Kyodo said. 
 
 The possible causes of upheaval in the North include an attack by an unnamed foreign force that triggers the collapse of the regime, sending civilians and soldiers across the border with China. 
 
 About 25,000 North Korean defectors have escaped across that border since the end of the 1950-53 Korean war. The heavily fortified border that has divided the Korean peninsula since the end of the conflict makes fleeing directly into South Korea practically impossible. 
 
 In the event of an influx of refugees, teams of Chinese officials and military personnel should be sent to border areas to question new arrivals from North Korea and block anyone believed to pose a threat to China’s national interest, the Kyodo report says. 
 
 “As foreign shows of force are out of our control, a situation could arise whereby our country faces an influx of military units via the border regions,” the documents reportedly said, according to the Daily NK website. 
 
 “There is concern that this circumstance could allow a foothold of resistance to form among refugees and breakaway soldiers. 
 
 “Under these circumstances teams must be dispatched to border regions including 'reconnaissance groups’ to assess the situation, 'investigation groups’ to question those who come into [China], 'blockade groups’ that prevent the influx of threats, and 'armed groups’ to defend against hostile powers.” 
 
 Military and political leaders would be confined separately to prevent them from directing further military action and to protect them from possible assassination attempts. 
 
 “Key figures must be moved to a separate investigation facility to ensure they cannot command any military activity nor band together with other forces [already in China],” the documents say. 
 
 Experts believe serious unrest in North Korea would send refugees flooding across its border with China. 
 
 While Beijing has expressed irritation with North Korea’s pursuit of a nuclear deterrent, it is keen to deter any threats to the regime. North Korea’s collapse would create a humanitarian crisis on its north-eastern border, while unification of the Korean peninsula could result in the unwanted presence of 28,500 US troops now based in South Korea on China’s doorstep. ||||| SEOUL/TOKYO (Reuters) - South Korean and Japanese jets joined exercises with two supersonic U.S. B-1B bombers above and near the Korean peninsula on Thursday, two days after North Korea sharply raised tension by firing a missile over Japan. 
 
 The drills, involving four U.S. stealth F-35B jets as well as South Korean and Japanese fighter jets, came at the end of annual U.S.-South Korea military exercises focused mainly on computer simulations. 
 
 “North Korea’s actions are a threat to our allies, partners and homeland, and their destabilizing actions will be met accordingly,” said General Terrence J. O’Shaughnessy, Pacific Air Forces Commander, who made an unscheduled visit to Japan. 
 
 “This complex mission clearly demonstrates our solidarity with our allies and underscores the broadening cooperation to defend against this common regional threat.” 
 
 North Korea has been working to develop a nuclear-tipped missile capable of hitting the United States and has recently threatened to land missiles near the U.S. Pacific territory of Guam. 
 
 On Monday, North Korea, which sees the exercises as preparations for invasion, raised the stakes in its stand-off with the United States and its allies by firing an intermediate-range missile over Japan. 
 
 On Thursday, its official news agency, KCNA, denounced the military drills in traditionally robust fashion, calling them “the rash act of those taken aback” by the missile test, which it described as “the first military operation in the Pacific.” 
 
 President Donald Trump, who has warned that the U.S. military is “locked and loaded” in case of North Korean provocation, reacted angrily to the latest missile test, declaring on Twitter that “talking is not the answer” to resolving the crisis over North Korea’s weapons programs. 
 
 U.S. Defense Secretary Jim Mattis was quick on Wednesday to stress that a diplomatic solution remained possible, but on Thursday he told reporters he agreed with Trump that Washington “should not be talking right now to a nation that is firing missiles over the top of Japan, an ally.” 
 
 White House spokeswoman Sarah Sanders reiterated at a regular briefing on Thursday that all options - diplomatic, economic and military - remained on the table. 
 
 Japanese Defence Minister Itsunori Onodera spoke to Mattis by telephone and agreed to keep putting pressure on North Korea in a “visible” form, Japan’s defense ministry said. Japanese Prime Shinzo Abe said he and visiting British Prime Minister Theresa May agreed to urge China, North Korea’s lone major ally, to do more to rein in North Korea. 
 
 May and Abe also discussed the possibility of adopting a new U.N. Security Council resolution on North Korea, a British government source said. 
 
 SANCTION OPTIONS 
 
 The 15-member U.N. Security Council on Tuesday condemned the firing of the missile over Japan as “outrageous” and demanded that North Korea halt its weapons programs. But the U.S.-drafted statement did not threaten new sanctions. 
 
 Two U.S. Air Force B-1B Lancer bombers fly from Andersen Air Force Base, Guam, for a mission, with an escort of a pair of Japan Self-Defense Forces F-15 fighter jets and U.S. Marines' F-35B fighter jets in the vicinity of Kyushu, Japan, in this photo released by Air Staff Office of the Defense Ministry of Japan August 31, 2017. Air Staff Office of the Defense Ministry of Japan/HANDOUT via REUTERS 
 
 Japan has been urging Washington to propose new Security Council sanctions, which diplomats said could target North Korean laborers working abroad, oil supplies and textile exports. 
 
 However, diplomats expect resistance from Russia and fellow veto-wielding power China, particularly given that new measures were only announced on Aug. 5 after North Korea tested its first two intercontinental ballistic missiles in July. 
 
 A U.S. ban on travel by Americans to North Korea comes into effect on Friday, a step announced after the death of a U.S. student shortly after his release from a 15-year prison sentence in the country, where three other Americans are still detained. 
 
 China repeated a call on Thursday for restraint by all parties. 
 
 Defence ministry spokesman Ren Guoqiang told a monthly briefing China would never allow war or chaos on the Korean peninsula, its doorstep, and military means were not an option. 
 
 “China strongly demands all sides to exercise restraint and remain calm and not do anything to worsen tensions,” Ren said, adding that Chinese forces were maintaining a normal state of alert along the North Korean border. 
 
 Chinese foreign ministry spokeswoman Hua Chunying said the situation on the peninsula was serious. 
 
 “The current tense situation on the peninsula isn’t a screenplay or a video game,” she told reporters. “It’s real, and is an immense and serious issue that directly involves the safety of people from both the north and south of the peninsula, as well as peace and stability of the entire region.” 
 
 Slideshow (12 Images) 
 
 For an interactive on North Korea's missile capabilities, click: here 
 
 For a graphic on North Korean missile trajectories, ranges, click: here 
 
 For a graphic on Kim's new act of defiance, click: here
– China is ramping up its military presence on its 880-mile border with North Korea in case a nuclear, economic, or military crisis sends millions of North Koreans fleeing in search of greener pastures, according to government websites. But as the Wall Street Journal reports, that might not be all China is preparing for. China's Defense Ministry hasn't referred to North Korea as the reason for a new border defense brigade along with a 24-hour video surveillance system, unit upgrades, new shelters and command posts, and recent live-fire and special forces drills in border regions; but experts say China could be preparing to intervene should the US attempt to seize nuclear weapons from its ally on the Korean Peninsula. Some aren't so sure China would be keen to take on the US and stress that recent enhancements at the border were first discussed last year. However, "once you start talking about efforts from outside powers, in particular the United States and South Korea, to stabilize the North ... you’re starting to look at a much more robust Chinese response," argues a former US defense official for East Asia. "If you’re going to make me place bets on where I think the US and China would first get into a conflict ... it’s the Korean Peninsula." Others note China will want to prevent US influence there to retain its regional power. In a column in May, retired Maj. Gen. Wang Haiyun wrote China should not only intervene in a Korean conflict but demand no US occupation of North Korean territory, though he said he did not speak for the government. He made similar comments in an op-ed in the state-owned Global Times in March, CNN reports.