North Korea blew up parts of its roads connected to South Korea on Tuesday, the military said, after vowing to cut off the roads and railways once seen as symbols of inter-Korean cooperation.

"North Korea has detonated parts of the Gyeongui and Donghae roads north of the Military Demarcation Line at around noon," the Joint Chiefs of Staff said.

The JCS said it has bolstered its surveillance and readiness posture.

Last week, the North's military announced a plan to "completely separate" North Korea's territory from South Korea, saying it had informed the US military of the move to "prevent any misjudgment and accidental conflict."

The Koreas are connected by roads and railways along the Gyeongui Line, which connects the South's western border city of Paju to the North's Kaesong, and the Donghae Line along the east coast.

The move came as North Korea has been ramping up inter-Korean tensions and wiping out traces of unification after its leader Kim Jong-un defined the Koreas as "two hostile states" late last year, with the country taking steps to dismantle inter-Korean land routes.

The North has since removed street lamps and installed mines along its side of the Gyeongui and Donghae roads, as well as deploying troops to build apparent anti-tank barriers and reinforce barbed wire within its side of the Demilitarized Zone separating the two Koreas.

Last week, JCS Chairman Adm. Kim Myung-soo told lawmakers that the Gyeongui and Donghae routes had been effectively cut off in August, noting that the military had been monitoring the North's activities.

Tensions have further heightened after North Korea claimed Friday that the South had sent drones over Pyongyang three times this month. Kim Yo-jong, the influential sister of the North Korean leader, warned the following day of a "horrible disaster" if South Korean drones are flown again over the North's capital.

South Korea has neither confirmed nor denied the claim and warned that the North will see "the end of its regime" if it causes any harm to South Koreans. (Yonhap)