North Korea vows to block and fortify border with South

North Korea said Wednesday it was moving to "permanently shut off and block the southern border."

It also vowed to "completely cut off roads and railways " leading to South Korea and "fortify the relevant areas of our side with strong defense structures," according to the North's official Korean Central News Agency (KCNA).

The North Korean military called its steps a "self-defensive measure" in response to South Korean "war exercises" and deployment of US strategic nuclear assets.

It also said it had sent a telephone message to US forces to "prevent any misjudgement" or "accidental conflict over the fortification process."

These measures are largely seen as a symbolic gesture, and it's unclear how they will affect Pyongyang's relations with South Korea, as cross-border travel and exchanges have been halted for years.

What was South Korea's reaction?

South Korea's military called the North's announcement a "desperate measure stemming from the insecurities of the failed Kim Jong Un regime."

Seoul will not tolerate any attempt by North Korea to change the status quo and will "overwhelmingly punish" Pyongyang for any provocations, the military said.

South Korean officials said earlier that North Korea had already been adding anti-tank barriers and reinforcing roads on its side of the border since April.

Pyongyang had spent months laying landmines and erecting barriers, turning the area into a wasteland, the officials said.

Seoul's spy agency has also detected signs that North Korea has demolished sections of a railroad linking the two Koreas.

Inter-Korean relations at a low point

With inter-Korean relations at their lowest point in many years, Pyongyang's announcement could be a possible first step toward more serious measures, such as amending the North's constitution to declare a new maritime border south of the current de facto line, some analysts expect.

KCNA said early Wednesday that the Supreme People's Assembly met for two days this week to change the legal age for North Koreans to work and vote in elections. Pyongyang also named No Kwang Chol as its new defense minister. 

However, state media made no mention of whether the meeting dealt with leader Kim Jong Un's January order to rewrite the constitution to remove the goal of a peaceful Korean unification, formally designate South Korea as the country's "invariable principal enemy" and define the North's sovereign, territorial sphere.

Kim's order stunned many North Korea watchers because it was seen as a break with his predecessors' long-held dreams of a unified Korea on the North's terms.

dh/wmr (AP, AFP, dpa)