South Korea called Thursday for a halt to a civic campaign to send anti-Pyongyang propaganda leaflets into North Korea, hours after the communist nation threatened to scrap a military tension reduction agreement and exchange projects unless Seoul stops the campaign.

The unification ministry also said it is planning to legislate a ban on such "tension-causing acts," arguing that the campaign causes danger to the lives and property of residents in border regions where the leaflets are sent via giant balloons.

"Actually, most of the leaflets have been found in our territory, causing environmental pollution and increasing burden on local people to get rid of them. ... Any act that could pose a threat to the life and property of those people should be stopped," ministry spokesperson Yoh Sang-key said.

"Taking into consideration relevant circumstances comprehensively, the government has already been mulling measures to fundamentally prevent such tension-causing acts near the border," he said.

Earlier in the day, North Korean leader Kim Jong-un's sister, Kim Yo-jong, issued a strongly worded statement condemning the leaflet campaign, saying good faith and reconciliation can never go together with such hostile activities.

"Clearly speaking, the 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 in the statement carried by the Korean Central News Agency.

"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 Mt. Kumgang, 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," she added.

Kim also said the summit agreements in 2018 and the military deal intended to stop all kinds of hostility and tension-raising action and the sending of anti-North Korea leaflets runs counter to such agreements.

She pointed her finger directly at the anti-Pyongyang leaflets sent across the border earlier this week by a group of North Korean defectors. The leaflets, totaling about 500,000 and carried by balloons, criticized the North's leader for threatening to take "shocking actual action with a new strategic nuclear weapon."

The leader's sister also called those defectors "human scum" and "rubbish-like mongrel dogs," urging South Korea to take every possible action, including enacting a law against such act without using "freedom of expression" as an excuse anymore.