North Korean soldiers appear to be mobilized for construction activities in the border area. Courtesy of Joint Chiefs of Staff

North Korea has been erecting anti-tank barriers along the inter-Korean border, according to the South Korean Joint Chiefs of Staff (JCS), Tuesday, in a move to fortify its defensive positions. Separately, it has been reinforcing roads and laying landmines in the frontline area despite casualties from mine explosions there.

"Since April, a large number of North Korean troops have been conducting various military works such as laying mines, reinforcing roads and installing what appear to be anti-tank barriers in frontline border areas, including the Northern Boundary Line, to strengthen security capabilities," a JCS official said.

"North Korea's activities seemed to be aimed at strengthening internal control, such as blocking North Korean troops and residents from defecting to South Korea."

A military official explained that anti-tank barriers built 2 kilometers north of the Military Demarcation Line (MDL) are intended to deter the advance of South Korean troops.

"The anti-tank barriers are approximately four to five meters tall and extend several hundreds of kilometers in length. North Korea has built those barriers in about four areas along the border," the official said.

The JCS also noted that several North Korean soldiers working in the Demilitarized Zone (DMZ) had been injured or killed in mine explosions, but the North's military appears to be moving ahead with its operations recklessly. It didn't specify when and how many casualties had been observed. The DMZ stretches for two kilometers on either side of the MDL.

Asked whether the barriers are expected to serve as a border, the official said, "Although we do not rule out that possibility, it is too early to judge whether North Korea is willing to build walls that separate them from the South. We are working closely with the U.N. Command to monitor whether North Korea's activities violate the Korean Armistice Agreement."

However, the official said it seems unlikely to halt North Korea's activities as the two Koreas have lost contact following the demolition of the inter-Korean liaison office in 2020.

"North Korean troops were spotted working tirelessly from sunrise to sunset. Even after casualties occurred, they continued on with their operations. Overall, thousands of soldiers are believed to have been mobilized in these activities," a JCS official said.

The JCS said 20 to 30 North Korean soldiers working there crossed the MDL within the DMZ on Tuesday and returned to their side after the South fired warning shots. This marks the second border crossing by North Korean troops this month after a similar incident occurred on June 9.

However, the military said the incident appeared to be "accidental," adding that there was no unusual activity after the warning shots.

This comes after North Korean troops were spotted installing mines and demolishing street lamps along land routes connecting the two Koreas in January and April, respectively, as inter-Korean relations have become increasingly strained in recent months.

Last December, North Korean leader Kim Jong-un said that inter-Korean relations had become "a relationship between two hostile countries and two belligerents at war," abandoning the goal of peaceful unification with the South.