North Korean defectors based in South Korea flew around 500,000 anti-Pyongyang propaganda leaflets via floating balloons to North Korea which angered the North and has risen tension between the two Koreas.

Kim Jong-Un's younger sister and North Korea's de facto leader of the Propaganda and Agitation Department, Kim Yo Jung issued a statement that urged Seoul to pass a law to prevent such propaganda activities.

She added that South Korea should "clear their house of rubbish."

"Those scums recklessly berated our utmost dignity [Kim Jong Un] and carelessly made fun of our nuclear ambitions," Kim Yo Jong condemned defectors sending leaflets to North Koreans through balloons.

Kim Yo Jong mentioned that North Korea would scrap a military agreement with Seoul and terminate a liaison office set up in 2018 if the defectors' activities failed to be contained.

North Korean defectors have been sending balloons from close to South Korea's demilitarized zone. Some of these balloons are almost 20 ft tall, long, transparent balloons with writings written vertically on them. The balloons typically carry anti-Pyongyang and anti-Kim leaflets with words that promote democracy, capitalism, and short Bible verses. 

Balloon propaganda campaigns in the Korean peninsula started as a distribution method since the Korean War. Originally they were organized by the governments and militaries of the Korean states but in modern days, they are mainly organized by South Korean non-governmental organizations that aim to send materials that are censored in North Korea.