A balloon presumably sent by North Korea is found in Namdong District, Incheon, June 10. Yonhap

Parasites have been detected in some of the trash-filled balloons sent by North Korea to South Korea, but no harmful substances were found, Seoul's unification ministry said Monday.

In recent weeks, North Korea has sent more than 1,000 trash-carrying balloons toward the South on multiple occasions in retaliation for South Korean activists' leaflet campaigns condemning the North Korean regime.

"Numerous parasites, such as roundworms, whipworms and threadworms, were found in the soil contained in the trash," the ministry said in a press release, adding that the parasites are believed to originate from human excrement.

The findings are based on an examination of 70 balloons.

Among the trash-filled balloons, torn pieces of clothing, such as neckties and blue jackets, which appeared to have been cut with scissors or knives, were also discovered. These clothes were identified as items previously provided to North Korea by a South Korean company.

"It appears that North Korea damaged and sent these previously supplied items to express extreme hostility toward the leaflet campaigns and to highlight the adversarial stance against South Korea," said a ministry official, who requested anonymity.

The official noted that most of the trash consisted of wastepaper and vinyl rather than ordinary household waste, suggesting that North Korean authorities might be trying to prevent the disclosure of the daily lives of North Koreans to the outside world.

For years, North Korean defectors in South Korea and conservative activists have sent anti-Pyongyang leaflets to the North using balloons, aiming to encourage North Koreans to rise up against the Kim family regime.

North Korea has strongly opposed these propaganda campaigns, fearing that an influx of outside information could threaten the leadership of its regime. (Yonhap)