North Korea would be held responsible for any damage incurred by its trash balloon campaign, South Korea‘s military warned Monday, a day after the North said South Korea should be ready to pay “a very high price” for sending anti-Pyongyang leaflets across the border.

The Joint Chiefs of Staff (JCS) issued the warning in response to a statement by Kim Yo-jong, the influential sister of North Korean leader Kim Jong-un, that claimed “dirty leaflets and things” had been discovered in 17 places in the border region and other areas of her country, and condemned such an act as “dirty play,” reports Yonhap news agency.