SEOUL, South Korea — North Korea said on Sunday its frontline military units are ready to launch attacks on South Korea, increasing pressure on its rival, which it said flew drones and dropped leaflets over the capital Pyongyang.

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

North Korea accused South Korea on Friday 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 on Sunday, the North’s Defense Ministry said the army had issued a preliminary operation order to artillery and other army units near the border with South Korea to “fully prepare to open fire.”

An unidentified ministry spokesman said the North Korean military has instructed relevant units to fully prepare for situations such as launching immediate attacks on unspecified enemy targets if South Korea again sends drones across the border infiltrates, which could potentially lead to fighting on the Korean Peninsula, according to the statement.

The spokesperson said there are “serious military tensions on the Korean Peninsula” over the South Korean drone launches. In a separate statement later Sunday, the spokesman said the entire South Korean territory “could turn into piles of ash” after the North’s powerful attack.

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

North Korea often releases such fiery, blistering rhetoric during times of heightened hostility with South Korea and the United States.

Ties between the two Koreas have remained tense since a US-led diplomacy over ending North Korea’s nuclear program collapsed in 2019. North Korea has since worked hard to expand its nuclear arsenal and has repeatedly threatened to attack South Korea and the US with its nuclear weapons. But experts say North Korea is unlikely to launch a full-scale attack as its military is overtaken by combined US and South Korean forces.

Observers predicted North Korea would escalate tensions ahead of next month’s U.S. presidential election to increase its influence over future diplomacy with the Americans.

Since May, North Korea has flown thousands of balloons containing waste into South Korea, in retaliation for South Korean activists piloting their own balloons with anti-Pyongyang leaflets. The South Korean military responded to the North Korean balloon campaign by restarting loudspeakers at the border to blare propaganda and K-pop songs to North Korea.

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