SEOUL — Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, vowed Sunday to respond to what she called a fresh South Korean civilian leafleting campaign, indicating North Korea would soon resume flying trash-carrying-balloons across the border.

Since late May, North Korea has floated numerous balloons carrying waste paper, scraps of cloth, cigarette butts and even manure toward South Korea on a series of late-night launch events, saying they were a tit-for-tat action against South Korean radicals scattering political leaflets via their own balloons.