Trash, toilet paper and suspected animal feces carried by balloons fell in South Korea near the North Korean border on Wednesday.

The filthy debris were sent by Pyongyang in retaliation for propaganda leaflets sent by South Korea across the border also by balloons.

“Tit-for-tat action will be also taken against frequent scattering of leaflets and other rubbish by the ROK near border areas,” Kim Kang Il, a vice-minister of defense, said in a statement Sunday, using the acronym for South Korea’s official name.

“Mounds of wastepaper and filth will soon be scattered over the border areas and the interior of the ROK and it will directly experience how much effort is required to remove them,” Kim said in the statement carried by the official Korean Central News Agency.

Photographs showing white balloons bearing garbage bags full of trash and what appeared to be excrement were shared widely by South Korean media.

Seoul’s Joint Chiefs of Staff said that “unidentified objects believed to be North Korean propaganda leaflets have been identified in the Gyeonggi-Gangwon border area and the military is taking action.”

“Citizens should refrain from outdoor activities, do not come into contact with any unknown objects, and report them to the nearest military base or police,” it said in a statement sent to Agence France-Presse.

It said that the North’s actions “clearly violate international laws and seriously threaten the safety of our people,” saying some of the balloons had contained suspected trash, which the military was checking.

“We sternly warn the North to immediately stop its inhumane and low-class actions,” it added.