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.

In a statement carried by state media Sunday, the North’s Defense 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.”

An unidentified ministry spokesperson said the North Korea’s military ordered relevant units to fully prepare for situations like launching immediate strikes on unspecified enemy targets when South Korea infiltrates drones across the border again, possibly triggering fighting on the Korean Peninsula, according to the statement.

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 separate statement later Sunday, the spokesperson said that the entire South Korean territory “might turn into piles of ashes” following the North’s powerful attack.

Also Sunday, the powerful sister of North Korean leader Kim Jong Un described as “suicidal” the South Korean Defense Ministry’s reported warning that North Korea would face the end of its regime if it harms South Korean nationals. She warned Saturday that the discovery of a new South Korean drone will “certainly lead to a horrible disaster.”

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 U.S.-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 U.S. with its nuclear weapons. But experts say it’s unlikely for North Korea to launch a full-blown attack because its military is outpaced by the combined U.S. and South Korean forces.

Observers predicted North Korea would escalate tensions ahead of next month’s U.S. presidential 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 songs to 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.