North Korea’s army has said it will sever road and railway access to South Korea and fortify areas on its side of the border, state media reported.

The Korean People’s Army said on Wednesday that it will “completely cut off roads and railways” linked to South Korea and “fortify the relevant areas of our side with strong defence structures”, according to the official Korean Central News Agency (KCNA).

The move was viewed as symbolic, given that cross-border travel and exchanges have been halted for years.

The army said in its statement carried by KCNA that it was a response to war exercises that have been held in South Korea as well as frequent visits by United States strategic assets to the region.

South Korea’s Ministry of Defence said in a statement that it had notified the US-led United Nations Command, a multinational military force that oversees affairs in the Demilitarized Zone (DMZ) between the two Koreas, which are still technically at war.

The two sides signed an armistice that ended fighting in the 1950-1953 Korean War, but not a peace treaty.

North Korea had already been installing landmines and barriers and creating wasteland along the heavily militarised border for months this year, South Korea’s military has previously said.

The new steps, which mark a further escalation of conflict between the two Koreas, were described in the army’s statement as a “self-defensive measure for inhibiting war and defending the security” of North Korea.

It said that “hostile forces are getting ever more reckless in their confrontational hysteria”, and that it had sent a message to the US military to explain its fortification activity to prevent any misjudgment and potential accidental clashes.

Tensions on the Korean Peninsula are at their highest point in years, with Pyongyang conducting a series of weapons tests. North Korea tested a long-range artillery system on Tuesday, KCNA reported.

The announcement came as Pyongyang maintained its silence on an expected revision of the constitution that will see the country scrap the goal of peaceful reunification and formally designate South Korea as an enemy state.

The Supreme People’s Assembly had been expected to make the constitutional changes during a two-day meeting this week, obeying orders from North Korean leader Kim Jong Un issued in January, which had raised concerns that all-out war could return to the Korean Peninsula.

But while KCNA reported that the country had appointed a new defence minister – No Kwang Chol, who accompanied Kim to talks with then-US President Donald Trump in 2018 and 2019 –  it made no mention of the constitutional amendments.

Some experts say North Korea might have delayed the constitutional revision, which would essentially ditch a landmark inter-Korean agreement signed in 1991, but others speculated it amended the constitution without announcing it because of its sensitivity.