South Korea's presidential office has warned of a "thorough crackdown" against campaigners sending anti-Pyongyang leaflets across the border, after North Korea expressed its fury over the campaigns.
Kim You-geun, a national security official at the Blue House in Seoul, said on Thursday that the campaigns did not help the "efforts to achieve peace and prosperity of the Korean peninsula".
Seoul's unification ministry also filed a legal complaint with the police against two defector groups for sending anti-Pyongyang leaflets across the border.
The ministry added that the two groups of North Korean defectors had "violated an agreement between the leaders of the North and the South and created tension."
The leaflets -- usually attached to hot air balloons or floated in bottles -- criticize North Korean leader Kim Jong-un on a regular basis over his nuclear ambitions.
North Korea has issued a series of vitriolic denunciations of the South since last week over sending anti-Pyongyang leaflets.
Officials in Seoul said they will consider a ban on leaflet launches after a recent statement on the campaigns from Kim Yo Jong, the younger sister and key adviser to the North Korean leader.
North has also warned South Korea of the possible scrapping of a recent inter-Korean military agreement if Seoul fails to stop North Korean defectors from sending propaganda leaflets into the Demilitarized Zone (DMZ) separating the two countries.
The Korean Central News Agency (KCNA) has described leaflet scattering as "an act of a preemptive attack that precedes a war".
South Korea's President Moon Jae-in earlier this week expressed "strong regret" over the leaflet launches, saying the government would mount a "thorough crackdown" against them.
The leaflet campaigns have long been a thorny issue between the two Koreas.
A thaw between the two Koreas began back in January 2018 when leaders from the two countries met, diplomatic visits were exchanged, and joint events were held.
South Korea also brokered diplomacy between the North and the United States. While incumbent US President Donald Trump met with Kim three times, interactions between Washington and Pyongyang gradually came to a halt over Trump’s refusal to relieve any of the harsh US sanctions on the North in spite of several major goodwill measures by Pyongyang.
The United States has been attempting to pressure the North into giving up its nuclear weapons program.
North Korea maintains that its nuclear and missile capabilities are intended to defend the country against potential aggression amid persisting joint war games by Seoul and Washington on the Korean peninsula.
The two Koreas remain technically at war since the 1950-1953 Korean War ended with an armistice rather than a peace treaty.