South Korea’s military says it has fired warning shots near its heavily fortified border with the North after Pyongyang blew up sections of the deeply symbolic roads linking the two countries.

At around midday, some parts of the road north of the military demarcation line (MDL) dividing the countries were blown up, South Korea’s Joint Chiefs of Staff said in a message sent to media on Tuesday.

In response, Seoul’s military “conducted counter-fire” in areas south of the MDL, it added later.

Since leader Kim Jong-un declared the South his country’s “principal enemy” earlier this year, the North has laid fresh mines, erected anti-tank barriers, and deployed missiles capable of carrying nuclear warheads along the already heavily fortified border.

Last week Pyongyang said it would permanently seal its southern border in response to war exercises held in South Korea and visits by US nuclear assets, and on Monday Seoul warned that Pyongyang was getting ready to blow up the roads.

Last week, North Korea also accused Seoul of using drones to drop anti-regime propaganda leaflets on the capital Pyongyang, with Kim convening a security meeting to direct a plan of “immediate military action” in response, state media reported Tuesday.

The roads and railways connecting the two countries have long been shuttered, but destroying them sends a clear message that Kim is not prepared to negotiate with the South, experts said.

“This is a practical military measure related to the hostile dual-state system that North Korea has frequently mentioned,” Yang Moo-jin, president of the University of North Korean Studies in Seoul, told AFP.

The North may be looking to erect more physical barriers along the border, Yang said, adding that the detonations could be “preparatory work for its construction of those walls”.

Seoul’s military initially denied sending drones north but has subsequently declined to comment, even as Pyongyang has blamed them directly, warning it would consider it “a declaration of war” if another drone was detected.

Activist groups have long sent propaganda northwards, typically by balloon, and enthusiasts are also known to have flown small, hard-to-detect drones into the North.

At Kim’s meeting on Monday, officials heard a report on the “enemy’s serious provocation”, said KCNA, adding Kim had “expressed a tough political and military stand”.

In 2022, five North Korean drones crossed into the South, the first such incident in five years, prompting the South Korean military to fire warning shots and deploy fighter jets.

The jets failed to shoot down any of the drones.

In July, Seoul said it would deploy drone-melting lasers this year, saying the South’s ability to respond to provocations would be “significantly enhanced”.

The new laser weapons – dubbed the “StarWars Project” by the South – shoot an invisible, silent beam that costs just 2,000 won ($1.45) per use, according to the Defense Acquisition Program Administration.

Relations between the two Koreas are at their lowest point in years, with the North’s army saying last week it would permanently shut the southern border by “completely cutting off roads and railways” connected to the South and building “strong defence structures”.

Following Kim’s meeting in Pyongyang, “attention is turning to whether North Korea will respond by sending drones into the South or take strong action if drones infiltrate its territory again”, said Cheong Seong-chang of the Sejong Institute.

“North Korea is likely to engage in strong provocations along the border if there is a recurrence of drone infiltrations,” Cheong told AFP.

Agence France-Presse and Reuters contributed to this report