(CNN) -- North Korea is raising the temperature on its neighbors, saying in its latest threat that it would not give any warning before any attack on South Korea. "Our retaliatory action will start without any notice from now," Pyongyang said in a statement published Tuesday by its official news agency, KCNA. North Korea said it was responding to what it called insults from the "puppet authorities" in the South, claiming that there had been a rally against North Korea in Seoul -- a rally it called a "monstrous criminal act." The renewed menacing rhetoric came a day after North Koreans celebrated the birthday of their country's founder, Kim Il Sung, who launched the Korean War.
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NEW: North Korea says U.S. calls for talks are "nothing but a crafty ploy" to shift blame
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North Korea says it would not give notice before attacking South Korea
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A U.S. Marine helicopter makes a hard landing in South Korea
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John Kerry says North Korea needs to show it is serious about denuclearization
"The conditions have to be met where the @placeholder has to move towards denuclearization, indicate a seriousness in doing so by reducing these threats, stop the testing and indicate it's actually prepared to negotiate," he said.