Authorities in South Korea found 260 balloons filled with trash on Tuesday.
The balloons were filled with cigarette butts, plastic bottles, paper and other rubbish.
This came weeks after South Korean officials received intelligence that North Korea was planning to harm South Korean diplomats.
In addition, at least 10 North Korean Christians have been sent to the country’s political prisons because they read the Bible, met with Christians or tried to reach South Korea.
They are among a group of 200 North Korean refugees who were returned from China last year.
After World War II, the Korean Peninsula was divided into two zones, known as South Korea and North Korea.
Prior to Korea’s division, North Korea’s city of Pyongyang, was popular for its Christian belief and had many churches.