South Korea said it has detected signs that North Korea is preparing to destroy the northern parts of inter-Korean roads no longer in use amid soaring tensions.

Monday’s statement follows a claim by North Korea 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 that it was observing various activities in North Korea that appeared to be preparations for demolishing the roads.

“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.

Mr Lee said that the South Korean military believes the North could also attempt to launch a space rocket, which is viewed by the UN as a banned test of long-range missile technology.

He said North Korea may conduct unspecified “small provocations” to ramp up pressure on Seoul.

The development comes as North Korea has 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 on Sunday, the North’s Defence Ministry said 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 is highly unlikely for the North to launch full-scale, pre-emptive attacks as its military is outmatched by the combined US 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 defence structures to cope with “confrontational hysteria” by South Korean and US 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 the south.

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 US expanding 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 US ahead of next month’s US presidential election.

In January, leader 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.

Mr 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 he likely aims to diminish South Korea’s voice in the regional nuclear standoff and seek direct dealings with the US. They say Mr Kim also likely hopes to diminish South Korean cultural influence and bolster his rule at home.