North Korea threatened on Friday to strike South Korean territory if anti-Pyongyang activists launch propaganda leaflets next week.
The South immediately vowed to retaliate, according to the Associated Press.
The North Korean military said it would launch a "merciless military strike" in response to the leaflets. It specifically warned residents near the area where activists launch the balloons carrying anti-Pyongyang leaflets to evacuate, the BBC reported.
"The moment a minor movement for the scattering is captured... a merciless military strike by the Western Front will be put into practice without warning," said the military in a statement.
South Korean Defense Minister Kim Kwang-jin said, "'If that were to happen, there will be a perfect response against the source of the attack," according to Yonhap news agency, Reuters reported.
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The New York Times noted, "The exchange of saber-rattling, though hardly unprecedented, comes at a politically sensitive time in South Korea, where a presidential election is to be held in December and parties are highly attuned to how a surprise North Korean move might affect the outcome."
The exchange of threats comes a day after South Korean President Lee Myung-bak visited an island which was shelled by the North two years ago and warned against provocation, the AP noted.
Glyn Davies, the top US envoy for North Korea, is also meeting with Lim Sung-nam, South Korea's envoy, over the stalled six-nation talks on North Korea's nuclear program.
Activists have sent leaflets across the border on many occasions, though North Korea has never retaliated with specific threats. Its statement on Friday said, "The leaflets are a most undisguised act of psychological warfare, a violation of the armistice and an intolerable act of war," according to The Times.
The two countries are still technically at war, since the 1950-53 Korean War ended without a peace treaty.
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