North Korea declares "state of war" against South Korea while United States plays it down Russia and China have urged North Korea and the United States to refrain from flexing their military muscle. NORTH Korea has announced it has entered a "state of war" with South Korea and will deal with every inter-Korean issue accordingly. The United States said it took the announcement "seriously," but noted it followed a familiar pattern, while South Korea largely dismissed it as an old threat dressed in new clothing. It was the latest in a string of dire-sounding pronouncements from Pyongyang that have been matched by tough warnings from Seoul and Washington, fuelling international concern that the situation might spiral out of control. "As of now, inter-Korea relations enter a state of war and all matters between the two Koreas will be handled according to wartime protocol," the North said in a joint statement attributed to all government bodies and institutions. "The long-standing situation of the Korean peninsula being neither at peace nor at war is finally over," said the statement carried by the official Korean Central News Agency (KCNA), adding that any provocation would trigger a "full-scale conflict and a nuclear war." The two Koreas have always technically remained at war because the 1950-53 Korean War concluded with an armistice rather than a peace treaty. The email from North Korea threatening to bomb US bases. The North had announced earlier this month that it was ripping up the armistice and other bilateral peace pacts signed with Seoul in protest against South Korea-US joint military exercises. People watch a TV news report showing North Korean leader Kim Jong Un, centre, and other leaders, at Seoul Railway Station in Seoul, South Korea, on Saturda. The White House labelled the latest statement from Pyongyang as "unconstructive" and, while taking it "seriously," sought to place the immediate threat level in context. "North Korea has a long history of bellicose rhetoric and threats and today's announcement follows that familiar pattern," said National Security Council spokeswoman Caitlin Hayden. In Seoul, the Unification Ministry insisted the war threat was "not really new." The Defence Ministry vowed to "retaliate thoroughly" to any provocation, but added that no notable troop movement had been observed along the border. Late on Saturday the North ratcheted up its threats, warning it could shut down the Kaesong industrial complex, a joint South-North venture that provides the regime with crucial hard currency. "We warn that stern measures will be taken if (South Korea) continues to make reckless remarks defaming our dignity," a state body said, adding that the fate of the complex depends entirely on the attitude of Seoul. Established in 2004 as a symbol of cross-border cooperation, Kaesong had managed to keep functioning despite repeated crises in inter-Korean relations. But there have been concerns that its operations would be affected by Pyongyang's move on Wednesday to sever a military hotline used to monitor movement in and out of the zone. People watch a TV news report showing North Korean army soldiers, at Seoul Railway Station in Seoul, South Korea, on Saturday. Most observers however still believe this will remain a verbal rather than a physical battle. "The North Koreans in recent weeks have turned rhetoric into performance art," said Gordon Flake, a Korea specialist and executive director of the Mansfield Foundation in Washington. "When they have already declared the armistice null and void, I do not think a declaration of war breaks new ground," Flake said. But he added that the situation had now become so volatile that any slight miscalculation carried the potential for rapid escalation. Both China and Russia have called for calm, with a Russian diplomat voicing particular concern on Saturday. "We expect all sides to show maximum responsibility and restraint and that no-one will cross the line after which there will be no return," Grigory Logvinov, a Russian foreign ministry pointman on North Korea, told the Interfax news agency. France on Saturday urged North Korea to refrain from any new provocation and return on the path of dialogue. Meanwhile Britain said threatening statements would only further isolate Pyongyang. A close-up of the 'attack plan'. The lettering on the map reads as "Strategic Forces' US Mainland Striking Plan." On Friday North Korean leader Kim Jong-Un ordered missile units to prepare to strike US mainland and military bases, after US stealth bombers flew over South Korea. The high-stakes standoff has its roots in North Korea's successful long-range rocket launch in December and the third nuclear test it carried out in February. Both events drew UN sanctions that incensed Pyongyang, which then switched the focus of its anger to the annual joint South Korea-US military drills. As tensions escalated, Washington has maintained a notably assertive stance, publicising its use of nuclear-capable B-52s and B-2 stealth bombers in the war games. The long-distance deployment of both sets of aircraft out of bases in Guam and the US mainland were intended as a clear signal of US commitment to defending South Korea against any act of aggression. Australian Foreign Minister Bob Carr condemned the latest round of threats and said Australia was considering imposing more sanctions on the rogue state. North Korean leader Kim Jong-Un discusses a strike plan with North Korean officers during an urgent operation meeting at the Supreme Command in an undisclosed location. Kim Jong-Un ordered preparations for strategic rocket strikes on the US mainland and military bases in the Pacific and South Korea. The lettering on the map, rear L, reads as "Strategic Forces' US Mainland Striking Plan." Picture: AFP Senator Carr said in a statement that reports from the Australian Embassy in Seoul suggest there is no immediate evidence of increased military preparations by North Korea. "Despite this, North Korea continues to pose a genuine threat to the safety of millions of people in our region," he said. Senator Carr has welcomed calls by China and Russia for restraint by all parties, as well as commitments by the United States regarding the defence of South Korea and Japan. Senator Carr has urged all nations to ensure existing measures are strictly enforced and said Australia is considering further "autonomous sanction" on North Korea. Earlier, North Korean media issued two photos that appear to show plans for striking the US mainland as tens of thousands rally for it. The pictures, released by the official Korean Central News Agency (KCNA), both showed leader Kim Jong-Un sitting at a desk in what looked like a dedicated military operations room. US B-2 stealth bomber flies over a US air base in Pyeongtaek, south of Seoul. The photos accompanied a KCNA report on an emergency meeting with top army leaders in which Kim ordered strategic rocket units to prepare for a possible strike against US mainland and Pacific bases. One picture showed Kim amongst four uniformed officers, but the main interest lay in the background. The left of the picture showed a map with the unambiguous title: "Strategic Forces' US Mainland Striking Plan." Straight lines on the map - not all of which was visible - appeared to show the proposed flight paths of missiles striking targets in the continental United States. North Korean army officers punch the air as they chant slogans during a rally at Kim Il Sung Square in downtown Pyongyang, North Korea. "I don't think this is a mistake," a South Korean defence ministry official told AFP. "I believe it has been intentionally made public, probably in order to distort facts about the North's military power," the official said. The pictures come as tens of thousands of North Korean soldiers and civilians held a huge rally and march in Pyongyang on Friday, in a mass display of support for a possible military strike against the United States. The rally in Pyongyang's giant Kim Il-Sung square was attended by soldiers, veterans, workers and students, all wearing military uniforms. The North's young leader, Kim Jong-Un, was not present. State television said the rally took place to support a decision issued by the Korean People's Army (KPA) supreme command on Tuesday - and ratified by Kim on Friday - to put the country's strategic rocket units on a war footing. "The statement was the ultimatum of the Korean People's Army against the US imperialists," an announcer said at the start of the rally. Under giant portraits of Kim's father Kim Jong-Il and grandfather Kim Il-Sung, the massed ranks of civilians and soldiers pledged their allegiance to the current leadership. South Korea's K-1 tanks take part in their military exercise in the border city between two Koreas, Paju, north of Seoul, South Korea. "Let's become guns and bombs for our respected leader Kim Jong-Un!," they chanted, pumping their fists in unison. The rally was addressed by military and party officials who urged North Korean troops to launch a "merciless strike" on the US mainland and US military bases in the Pacific and South Korea. "We are all ready to wipe them out for our final victory," army officer Kwon Yong-Chol said. US Defence Secretary Chuck Hagel said Washington would not be cowed by Pyongyang's bellicose threats and stood ready to respond to "any eventuality." His comments came as nuclear-capable US B-2 stealth bombers were deployed in ongoing US joint military drills with South Korea. The B-2 flights, which followed training runs by B-52 bombers, were part of annual drills which North Korea each year denounces as rehearsals for war.