The balloons carried toilet paper, batteries and suspected poo into two border provinces.
Photographs shared on social media show bags attached via string to white translucent balloons carrying toilet paper, dark soil, and batteries, among other contents.
Police and military officers are seen in some of these photographs.
South Korea's Yonhap news agency reported that "some of the fallen balloons carried what appears to be faeces judging from its dark colour and odour".
South Korea's military condemned the act as a "clear violation of international law".
The problem with news about North Korea is that tabloids and defectors can literally just make shit up and it will be republished uncritically by "respectable" news sources so you have no way to judge its credibility.
Or maybe it's all true, and to get between cities, north koreans have to pull the train to the next city. Which is actually a fake city, surrounded by fake farms, attended by fake farmers. Then they steal hollywood movies and are immediately executed by anti-aircraft gun for watching western media.
Do you have a rental storage place around you that offers 10 dollars a month intro pricing? You can just leave your garbage there. Pay one month, cash, and never come back.
"It seriously threatens the safety of our people. North Korea is entirely liable for what happens due to the balloons and we sternly warn North Korea to immediately stop this inhumane and crass action," the military said.
It does not help South Korea when they make silly statements like this.