South Korea on Sunday vowed a “firm response” against possible provocations by North Korea, which threatened Sunday to take military action if a civic group here pushed ahead with its plan to send anti-Pyongyang fliers across the border.

“We sternly warn against the North’s threats. ... Should the North proceed with its provocations across the military demarcation line, our military will react in a strong and stern manner,” the Joint Chiefs of Staff said in a statement. It reiterated that the leaflet campaign falls under the freedom of expression, a basic civil right, and thus cannot be forcibly regulated.

Earlier in the day, North Korea renewed its threat against the South Korean civic group’s plan to send thousands of anti-Pyongyang leaflets into the hermit kingdom. The group, consisting of North Korean defectors, plans to use hot-air balloons to scatter thousands of leaflets along with copies of the U.S. comedy film “The Interview,” which depicts the fictional assassination of North Korean leader Kim Jong-un.

North Korea warned it will shoot down the balloons and vowed to “strike those who aggravate inter-Korean tensions.” It said South Koreans living near the inter-Korean border should evacuate after the leaflets are sent.

Pyongyang said distributing the movie “The Interview” was “a grave provocation and effectively an act of war,” adding that South Korea would have to take blame for “the catastrophic aftermath” of the leaflet campaign.

A similar scuffle took place last October, when both sides exchanged fire after balloons carrying anti-North Korea leaflets were launched into the communist country. No casualties or property damage were reported.

The two Koreas technically remain at a state of war, after the 1950-53 Korean War ended in a cease-fire, instead of a peace treaty.

By Yoon Min-sik (minsikyoon@heraldcorp.com)