"The indiscriminate nuclear strike to be made by the DPRK will clearly show those keen on aggression and war the military mettle of Juche Korea," it said. "Juche Korea" is the official ideology of North Korea which relates to self-reliance.
It also said it had a military operation plan to "liberate South Korea" and "strike the U.S. mainland."
The statement comes after 15,000 American Marines arrived in South Korea last week for military drills with South Korean troops designed to test their ability to respond to any potential attacks from the North.
South Korean news agency Yonhap said the drills, called the Key Resolve and Foal Eagle exercises, which begin Monday, involve more than 300,000 South Korean troops and include the use of the U.S. Navy's nuclear-powered aircraft carrier USS John C. Stennis, as well as U.S. military aircraft.
North Korea sees the exercises, which are carried out annually, as a precursor to invading its territory and said the "the army and people of the DPRK will launch an all-out offensive to decisively counter the U.S. and its followers' hysteric nuclear war moves to plunge the space of the DPRK's existence into a nuclear disaster, not content with wantonly encroaching upon the sovereignty and security of the dignified DPRK."
It's not the first time that North Korea has issued such threats but the latest statement comes at a time of particularly fraught tensions between North Korea and the rest of the world.
In January, the regime said it had successfully tested its first hydrogen bomb, flouting a worldwide ban on nuclear testing. That led to international condemnation, even from China which has been a stalwart ally of North Korea. Its opposition to the testing showed that even it could be tiring of North Korea's provocations.
Responding to the latest threat, Moon Sang-gyun , a spokesman for South Korea's Defense Ministry said that "North Korea must stop its rash and reckless behavior."
"We will respond resolutely and mercilessly if the North ignores our warning and attempts a provocation," he added.
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