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, signalling 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 activists scattering political leaflets via their own balloons. No hazardous materials have been found. South Korea responded by suspending a 2018 tension-reduction deal with North Korea and resumed live-fire drills at border areas.