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 the 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 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.
The explosions came a day after North Korean leader Kim Jong Un called a meeting with his top military and security officials to discuss the 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 earlier on Tuesday.
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 would be 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 a peaceful Korean unification.
In 2020, North Korea blew up the 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.