The Joint Chiefs of Staff said these trash bundles are expected to move toward the Seoul metropolitan area and surrounding Gyeonggi Province, considering the direction of the wind, Yonhap news agency reported.

North Korea had last floated balloons on October 24. It has done so on 31 occasions since late May in retaliation against anti-Pyongyang propaganda leaflets sent across the border by activists in the South.

On Sunday, Kim Yo-jong, the powerful sister of North Korean leader Kim Jong-un, claimed that South Korean leaflets had crossed the border into the North the previous day and warned that Seoul would have to pay"a dear price" for such action.