SEOUL, South Korea — North Korea likes to call South Korea a land of “political filth” and its leaders, including President Park Geun-hye, “human trash.” Now, apparently to highlight its contempt, it has begun sending balloons into the South with an unusual payload, the police here said on Thursday: cigarette butts.

North and South Korea have escalated their propaganda war across their heavily armed border since Jan. 6, when the North conducted its fourth nuclear test.

The South turned on high-powered loudspeakers to blare pop songs and harsh criticism of the North’s leader, Kim Jong-un, across the border. The North began sending balloons into the South loaded with leaflets.

The balloons were timed to detonate their payloads, scattering thousands of messages that, among other things, called Ms. Park a “filthy president.”