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.

"I once again emphasise that all responsibility lies in North Korea should South Korean citizens suffer any damage from the North's trash-carrying balloons," JCS spokesperson Colonel Lee Sung-jun said.

Noting a rare photo released by the North's state media that showed leaflets flown in from South Korea being burned, along with a pack of cold medicine, Lee said it simply depicts how North Korea is reacting to supplies that were sent for humanitarian support.

Since late May, North Korea has sent more than 2,000 trash-filled balloons into the South, in a tit-for-tat move against anti-Pyongyang leaflets sent by North Korean defectors in the South. South Korea responded by blaring anti-Pyongyang broadcasts through its border loudspeakers.

On whether to resume the loudspeaker broadcasts, the JCS spokesperson said the military will take a "flexible" approach, based on unspecified strategic and operational circumstances.