“Preparations are being made to blow up the road,” JCS spokesperson Col. Lee Sung-jun said. “It is possible [for the explosions] to take place as early as today.”

North Korea’s military said Wednesday that it is permanently sealing off its border with South Korea, cutting off all rail and road connections and bolstering defensive fortifications, as tensions continue to rise on the Peninsula.

The North has sent thousands of trash-carrying balloons across the border in recent months and Seoul has responded with loudspeaker propaganda broadcasts at the DMZ.

On Friday, the North accused South Korea of flying drones carrying leaflets in the skies over Pyongyang three times in the previous week. In a follow-up statement, its military announced that orders were given “to place eight artillery brigades fully armed at full wartime strength on standby to open fire,” according to the official Korean Central News Agency.

Kim Yo Jong, the influential sister of North Korean leader Kim Jong Un, warned Sunday that any further drone flights would “certainly lead to a horrible disaster.”

South Korea’s Defense Ministry responded in a statement to reporters saying any attempts to harm its people by the North “will be the end of the North Korean regime.”

The Joint Chiefs of Staff said Friday it could not confirm whether the military had sent drones over the border to the North, which Col. Lee repeated on Monday.

The spokesman said that the South Korean military is monitoring activity by the North’s artillery units at the border as well as any other possible moves such as the launch of a space vehicle.

“Our military is keeping a close eye on North Korean military movements and is fully prepared for the possibility of an actual provocation,” Lee said.

“All of this [situation] has come from North Korea, and we strongly warn North Korea to stop the filthy and low-grade garbage balloons,” he added.