SEOUL, South Korea (AFP)— North Korea confirmed that it has blown up sections of roads and railways leading to South Korea, calling it a “hostile state”, North Korean state media reported Wednesday.

Confirming an account from the South Korean military, the Korean Central News Agency (KCNA) said the transport links “have been completely blocked through blasting”.

Pyongyang’s military last week vowed to permanently seal its southern border after spending months laying mines and building anti-tank barriers in the wake of leader Kim Jong Un declaring the South his country’s “principal enemy”.

The North 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.

Referring to the destruction of the roads and railways, KCNA said “this is an inevitable and legitimate measure” that follows the North Korean constitution “which clearly defines the ROK as a hostile state”, referring to the South’s official name, the Republic of Korea.

North Korea recently amended its constitution and this was the first such mention of the charter formally declaring South Korea to be an enemy state, the Yonhap news agency said.

The deeply symbolic transport infrastructure linking the two countries has long been shuttered, but destroying it sends a clear message that Kim is not prepared to negotiate with the South, experts said.

KCNA said the blasting targeted 60-metre sections of roads and railways in the east and west sections of the border with South Korea.

The agency said this measure was taken “due to the serious security circumstances running to the unpredictable brink of war owing to the grave political and military provocations of the hostile forces.”

On Tuesday, South Korea’s military released video footage showing North Korean soldiers in military uniforms ahead of a huge explosion, which emitted thick billowing smoke as it blew up sections of what is known as the Gyeongui road.

More footage, apparently from after the blasts, showed excavators digging, while soldiers worked as large red trucks arrived.

South Korea’s unification ministry slammed the North for what it called an “extremely abnormal” provocation, adding that Seoul had shouldered millions in costs for building the infrastructure.

“North Korea still has repayment obligations regarding this funding,” it added.

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.

Later Tuesday, Kim’s powerful sister released a statement, saying Pyongyang has secured “clear evidence” that the South Korean military was behind the drones that reached Pyongyang.