North Korea says it won't warn South Korea before an attack

(CNN) -- North Korea upped the temperature on its neighbors on Monday, warning in a new threat that it would not give any advance notice before attacking South Korea.

"Our retaliatory action will start without any notice from now," Pyongyang said in a statement carried 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.

It called the rally a "monstrous criminal act."

The renewed threats came as North Koreans celebrated the birthday of their country's founder, Kim Il Sung, who launched the Korean War.

Earlier Monday, U.S. Secretary of State John Kerry urged the regime in Pyongyang to ditch its nuclear program and put a lid on its fiery rhetoric if it wants to hold talks.

"The United States has made clear many times what the conditions are for our entering talks and they haven't changed," Kerry said during an interview with CNN's Jill Dougherty in Tokyo.

"The conditions have to be met where the North 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.

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