China's People's Liberation Army is on high alert and making contingency plans for a further escalation of tension on the Korean Peninsula, dpa quoted a source with close ties to the Chinese military as saying. PLA generals were concerned about the security of North Korean nuclear facilities and the possibility of an influx of refugees into China, said the source, who recently met several generals. "The generals are very much concerned," the source said Wednesday, speaking on condition of anonymity. They also worried that North Korea's recent sabre-rattling could lead to accidental military confrontation that would see the Korean Peninsula "up in flames." The contingency plans included the possibility that Chinese forces could cross into North Korea, if a clash breaks out, to secure nuclear facilities and prevent any nuclear disaster. "Nobody talks about the danger that something like Fukushima might happen in North Korea," the source quoted a general as saying. The PLA was also planning how to handle a potential influx of refugees across China's 1,400-kilometre border, the source said. Unconfirmed reports said China had reinforced its troops near the North Korean border, but the Chinese government has declined to comment. Some Chinese and South Korean analysts expressed concern that North Korean leader Kim Jong Un lacked experience and could be manipulated into confrontation with the United States and South Korea by the much older military leaders who advise him. "Kim Jong Un is dangerous," said Kim Heung Kyu, a political scientist at Sungshin Women's University in Seoul. "He is young, inexperienced and eager to show his people how great he is." North Korea on Thursday said it had authorized its military to attack US targets, including by nuclear weapons, and reportedly moved a mid-range missile to its east coast. "I don't think they are capable to launch this kind of attack against the US," Kim said earlier this week. "They will target military areas or certain scientific facilities, which would cause tremendous trouble." Pyongyang Tuesday it would restart "without delay" a 5-megawatt reactor in the north-western city of Yongbyon, used for enriching weapons-grade plutonium. China, traditionally the isolated regime's main diplomatic ally, expressed "regret" at the announcement. "Currently, the situation on the [Korean] peninsula is sensitive and complicated," Foreign Ministry spokesman Hong Lei told reporters. "We appeal to relevant parties to remain calm and exercise restraint, return to the track of dialogue and consultation as soon as possible, and jointly seek ways to resolve the issue."