Pyongyang accused South Korea of sending a drone into North Korean territory.
North Korea has said it had found the remnants of a South Korean military drone and that any further "violation" of its territory would result in a "declaration of war."
Tensions between the two sides of the peninsula have escalated since May when the North began flying balloons carrying garbage across the border to the South, prompting Seoul to respond by restarting loudspeaker propaganda broadcasts.
Ah, you see, we received intel from China that the South's first order of business when they invade us is to destroy these railways. Now we, as to be one step ahead as always, decided to take preliminary actions. This is how you disrupt enemy planning, watch and learn you people.