SEOUL - Propaganda balloons carrying signs denouncing "liar Kim Jong Un" and his new strategic nuclear weapons floated across the demilitarised zone towards North Korea late last month, released by defectors who said they wanted to expose the bad deeds of the dictator.

The move incurred the wrath of his sister Kim Yo Jong, who slammed the leaflets as a "despicable act" and threatened to scrap an inter-Korea military agreement, abolish a joint liaison office and shut down major exchange projects.