The balloons have been a common activist tactic for years,but North Korea considers it an attack on its government. Defectors and other activists in recent weeks have used the leaflets to criticise the North's authoritarian leader Kim Jong-un over his nuclear ambitions and dismal human rights record.
While Seoul has sometimes sent police officers to block such activities during times of high tension,it had resisted the North's calls to fully ban them,saying the activists were exercising their freedoms.
The shift followed remarks earlier in the morning from Kim's powerful sister,who threatened to end the military agreement and said the North could permanently shut a liaison office and an inter-Korean factory park that have been major symbols of reconciliation.
In her statement released through state media,Kim Yo-jong called the defectors involved in the balloon launches"human scum"and"mongrel dogs"who betrayed their homeland and said it was"time to bring their owners to account",referring to the government in Seoul.
"[South Korean] authorities will be forced to pay a dear price if they let this situation go on while making sort of excuses,"she said.
"If they fail to take corresponding steps for the senseless act against the fellow countrymen,they had better get themselves ready for possibility of the complete withdrawal of the already desolate Kaesong Industrial Park following the stop to tour of[Diamond Mountain],or shutdown of the[North-South] joint liaison office whose existence only adds to trouble,or the scrapping of the[North-South] agreement in military field which is hardly of any value."