North Korea threatens to send troops into demilitarised zone as tensions with South Korea intensify

North Korea's military is considering sending troops into a demilitarised buffer zone it shares with the South, as relations between the two nations "turn worse and worse".

Tensions have escalated in recent weeks after North Korean defectors fled to the South, who alongside activists have been flying anti-North Korea propaganda brochures back over the border via balloons.

While South Korea has promised to pursue legal action against those responsible for the brochures, the North is not appeased and says it's now "mapping out military action plans" as it plots the best way to retaliate.

"Our army is keeping a close watch on the current situation in which the north-south relations are turning worse and worse," the Korean People's Army (KPA) said in a statement to the Korean Central News Agency (KCNA).

"The KPA is studying an action plan for taking measures to make the army advance again into the zones that had been demilitarised under the north-south agreement, turn the frontline into a fortress and further heighten the military vigilance against the south.

"We will map out the military action plans for rapidly carrying out the said opinions to receive approval from the Party Central Military Commission."

North and South Korea share a demilitarised zone which serves as a buffer between the two nations. This is the area that the North is threatening to occupy with troops.

Last week, Kim Yo-jong - North Korean leader Kim Jong-un's sister, who also serves in an unofficial capacity as one of his top aides - threatened a "decisive" action against South Korea over the brochures.

However, some analysts say North Korea is simply using the brochures to pile pressure on South Korea and attract the attention of the US, who have implemented harsh sanctions against them after nuclear talks stalled last year.