SEOUL, South Korea (AP) — South Korea said Monday it has detected signs that North Korea is preparing to destroy the northern parts of inter-Korean roads no longer in use, as the rivals are embroiled in soaring tensions over North Korea’s claim that South Korea flew drones over its territory.

Destroying the roads would be in line with leader Kim Jong Un’s push to cut off ties with South Korea and formally cement it as his country's principal enemy.

South Korea's military said Monday that it was observing various activities in North Korea that appeared to be preparations for demolishing the roads, such as installing screens.

“They have installed screens on the road and are working behind those screens, preparing to blow up the roads,” Lee Sung Joon, spokesperson of South Korea’s Joint Chiefs of Staff, told a briefing. He said the demolitions could be carried out as early as Monday.

Lee said that the South Korean military believes that the North could also attempt to launch a space rocket, which is viewed by the U.N. as a banned test of long-range missile technology. Lee said North Korea may conduct unspecified “small provocations” to ramp up pressure on Seoul.

It’s not clear how much parts of the roads North Korea would destroy.

The development comes as North Korea has recently 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 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.” The spokesperson said that the entire South Korean territory “might turn into piles of ashes” following the North’s powerful attack.

North Korea often releases warlike rhetoric when animosities with its rivals increase. Experts say it's highly unlikely for North Korea to launch full-scale, preemptive attacks as it military is outmatched by the combined U.S. and South Korean forces.

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.

Last week, North Korea said it will permanently block its border with South Korea and build front-line defense structures to cope with “confrontational hysteria” by South Korean and U.S. forces.

South Korean officials said North Korea had already been adding anti-tank barriers, planting mines and reinforcing roads on its side of the border since earlier this year in a likely attempt to boost its front-line security posture and prevent its soldiers and citizens from defecting to South Korea.

Tensions on the Korean Peninsula are at their highest point in years, with North Korea continuing a run of provocative weapons tests and South Korea and the U.S. expanding their military drills.

Destroying the roads and engaging in other provocations could be seen as a move to dial up pressure on South Korea and the U.S. ahead of next month’s U.S. presidential election.

In January, Kim Jong Un ordered the revision of North Korea's constitution to remove the goal of a peaceful Korean unification, formally designate South Korea as the country’s “invariable principal enemy” and define the North’s sovereign, territorial sphere.

Kim’s order stunned many North Korea watchers because it was seen as breaking away with his predecessors’ long-cherished dreams of peacefully achieving a unified Korea on the North’s terms. Experts say Kim likely aims to diminish South Korea’s voice in the regional nuclear standoff and seek direct dealings with the U.S. They say Kim also likely hopes to diminish South Korean cultural influence and bolster his rule at home.