North Korea appears to be preparing to carry out explosions at roads connected to South Korea, the South's military said Monday, just days after Pyongyang vowed to cut off all inter-Korean roads and railways.

On Wednesday, the North's Korean People's Army announced the measure that will "completely separate" North Korea's territory from that of South Korea and said it sent a telephone message to the US military in the South to "prevent any misjudgment and accidental conflict over the fortification project."

"Following an announcement by the KPA on Oct. 9, the North Korean military has been carrying out activities assumed to be linked to explosions on the roads along the Gyeongui and Donghae lines," the Joint Chiefs of Staff said.

The JCS said it is closely monitoring such activities that are taking place north of the Military Demarcation Line and seeking safety measures for troops and South Korean people.

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 latest 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" last year and has taken steps to eliminate the routes once seen as symbols of inter-Korean exchange and cooperation.

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

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

South Korea's defense ministry declined to confirm the claim, citing strategic issues, and warned that the North will see "the end of its regime" if it causes any harm to South Koreans. (Yonhap)