North Korea said its front-line army units are ready to launch strikes on South Korea, ramping up pressure on its rival that it said flew drones and dropped leaflets over its capital Pyongyang.

South Korea has refused to confirm whether it sent drones but warned it would sternly punish North Korea if the safety of its citizens is threatened.

North Korea on Friday accused South Korea of launching drones to drop propaganda leaflets over Pyongyang three times this month and threatened to respond with force if it happened again.

North Korea has floated thousands of balloons carrying rubbish towards the border with South Korea (Lee Jin-man/AP)

In a statement carried by state media on Sunday, the North’s Defence Ministry said that the military had issued a preliminary operation order to artillery and other army units near the border with South Korea to “get fully ready to open fire”.

A ministry spokesperson said North Korea’s military ordered relevant units to fully prepare for situations including launching immediate strikes on unspecified enemy targets if South Korea sends drones across the border again, possibly triggering fighting on the Korean Peninsula.

The spokesperson said that “grave touch-and-go military tensions are prevailing on the Korean Peninsula” because of the South Korean drone launches.

In a further statement issued on Sunday, the spokesperson added that the entire South Korean territory “might turn into piles of ashes” following a powerful attack from the North.

Elsewhere on Sunday, the powerful sister of North Korean leader Kim Jong Un described the South Korean Defence Ministry’s reported warning that North Korea would face the end of its regime if it harms South Korean nationals as “suicidal”.

Kim Yo Jong warned that the discovery of any new South Korean drone over Pyongyang would “certainly lead to a horrible disaster”.

Kim Yo Jong, the sister of North Korean leader Kim Jong Un, warned that the discovery of new South Korean drones in the North could ‘lead to a horrible disaster’ (Jorge Silva/Pool Photo via AP)

North Korea often issues such fiery, blistering rhetoric in times of elevated animosities with South Korea and the United States.

Ties between the two Koreas remain tense since a US-led diplomacy on ending North Korea’s nuclear program fell apart in 2019.

North Korea has since pushed hard to expand its nuclear arsenal and repeatedly threatened to attack South Korea and the US with its nuclear weapons. But experts say it is unlikely North Korea would launch a full-blown attack because its military is outpaced by the combined US and South Korean forces.

Observers predicted North Korea would escalate tensions ahead of next month’s US election to boost its leverage in future diplomacy with the Americans.

Since May, North Korea has floated thousands of balloons carrying rubbish toward South Korea in retaliation for South Korean activists flying their own balloons carrying anti-Pyongyang leaflets.

South Korea’s military responded to the North’s balloon campaign by restarting border loudspeakers to blare broadcast propaganda and K-pop into North Korea.

North Korea is extremely sensitive to any outside criticism of the authoritarian government of Kim Jong Un and his family’s dynastic rule.