Latest move comes after Pyongyang accused South Korea of sending drones carrying propaganda leaflets over its capital.
North Korea has blown up the northern sections of disused roads that connect it to South Korea, according to South Korea’s military.
Some parts of the road north of the military demarcation line dividing the two countries were blown up at about midday (03:00 GMT), the Joint Chiefs of Staff said in a message sent to media on Tuesday.
The military fired warning shots south of the demarcation line, it said.
Seoul had warned on Monday that Pyongyang was preparing to blow up the roads.
Tensions on the Korean Peninsula have risen since North Korea accused its neighbour of sending drones carrying propaganda leaflets over the country’s capital Pyongyang.
South Korea’s military later released video footage of the blasts.
One showed North Korean soldiers in military uniforms setting up what appeared to be cameras on tripods ahead of a huge explosion, which blew up sections of the Gyeongui road and kicked up billowing clouds of smoke and dust. More footage, apparently from after the blasts, showed excavators digging, while North Koreans in military uniforms worked nearby. There was also footage showing North Korea blowing up a section of the Donghae road, on the east coast.
While the two roads have long been closed, analysts say their destruction indicates that North Korean leader Kim Jong Un is no longer willing to negotiate with South Korea.
“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 the AFP news agency.
The blasts came a day after Kim called a meeting with his top military and security officials to discuss the drone issue.
During the meeting, Kim described the flights as the “enemy’s serious provocation” and laid out unspecified tasks related to “immediate military action” and the operation of his “war deterrent” for defending the country’s sovereignty, North Korean state media reported on Tuesday morning.
North Korea earlier put frontline artillery and other army units on standby to launch attacks on South Korea, if its drones were found over North Korea again. South Korea has refused to confirm whether it sent drones but warned it would sternly punish North Korea if the safety of its citizens was threatened.
Destroying the roads is in line with Kim Jong Un’s push to cut off ties with South Korea, formally cement it as his country’s principal enemy and abandon North Korea’s decades-long objective to seek the peaceful unification of the two Koreas.
In 2020, North Korea blew up the empty liaison office for the two Koreas, signalling the end of a period of detente.
In November last year, Pyongyang said it would move more troops and military equipment to the border and would no longer be bound by a 2018 joint military agreement after Seoul suspended parts of the agreement in response to Pyongyang’s launch of a military spy satellite.
South Korean officials have said that North Korea began adding antitank barriers and laying mines along the border earlier this year.