North Korea appears to build fence south of MDL, raising DMZ clash fears

North Korea appears to have installed a fence south of the military demarcation line (MDL) in the central sector of the inter-Korean border for the first time. As fears grow that its accelerating fortification work could eventually lead to armed clashes between the two Koreas, Seoul also reported that it successfully test-launched a domestically developed hypersonic glide vehicle (HGV) for the first time in what seems like an indirect warning towards Pyongyang.

South Korean military intelligence spotted the structure in recent imagery and is still analyzing it, according to the National Assembly's defense committee and military sources on Thursday. 

This is the first time a North Korean fence is believed to have crossed the MDL since the North began fortifying the border in April 2024. Until now, the closest North Korean fence identified was about 80 meters (262 feet) north of the MDL.

“A minefield appears to have been laid south of the fence,” a National Assembly official said.

In the area, the minefield is the southernmost of the three features, with a strip cleared of vegetation just north of it. The fence sits north of that strip, and the military has assessed that it lies south of the MDL as South Korea defines it. The Joint Chiefs of Staff (JCS) said, however, that a joint on-site investigation with the United Nations Command is needed to confirm whether the structure is in fact a fence.

North Korea's fortification work along the border is advancing quickly, particularly on the western and central fronts. With vegetation along the MDL nearly cleared, the North is now laying mines and building fences behind them. The work usually follows a set sequence, though it varies by terrain: clearing the land, laying mines, putting up triple fences and building tactical roads. Along major roads near the demilitarized zone's (DMZ) northern boundary, the North is also installing antitank barriers.

The concern is that North Korean troops could cross the MDL more frequently as the fortification work progresses. In the area under the Army's 21st Infantry Division on the eastern front, four to five armed North Korean guards cross the MDL almost daily along paths created by the clearing work, according to military sources. By treating the fortification zones as guard and patrol routes, North Korean troops have pushed their activity south of the MDL, and observers say similar movements could emerge along the new fence line on the central front.

Fears of accidental clashes are also rising as the two Koreas jockey for control of the DMZ following the recent mine blast on the western front.

North Korea has repeatedly said since the blast that it will hold to the MDL as it defines it. In a statement from Pyongyang's foreign ministry, the North threatened to respond immediately and forcefully to any violation of its territory, however small. If the South Korean military moves to tear down the fence south of the MDL after removing North Korean mines, the North is likely to call it a “territorial violation” and respond.

Amid rising tensions, the Blue House said in a written briefing Thursday that a domestically developed HGV had been successfully test-launched for the first time, with President Lee Jae Myung in attendance. The government has been considering shows of force against North Korea in response to the mine blast, and the disclosure of the new weapon is seen as an indirect warning to Pyongyang.

“It is significant in that we have fully secured a new deterrent capable of precisely striking key targets in the battlefield environment of the Korean Peninsula,” the Blue House said.

An HGV rides a ballistic missile booster to the upper atmosphere, separates from it and glides at low altitude. Because it maintains speeds of Mach 5, or about 6,100 kilometers per hour (3,790 miles per hour), or faster and flies an unpredictable path, it is difficult for existing missile defenses to detect and intercept.

The Blue House also disclosed that Lee had inspected the Hyunmoo-5 surface-to-surface missile, dubbed the “monster missile” for its massive weight and destructive power.

Meanwhile, the DMZ also came under scrutiny at the National Assembly on Thursday, where lawmakers at the defense committee's annual parliamentary audit of the JCS questioned why the military's first on-site survey in the DMZ had been moved from the area under the 21st Division on the eastern front to the area under the 25th Division on the western front.

“In consultations with the UN Command in April, we set the 21st Division as the first priority and the 25th Division as the second, but in August, we switched to the 25th Division after considering the weather, terrain and close-range enemy activity,” Gen. Lee Sang-ryeol, commander of the Army's Ground Operations Command, said in response to a question from People Power Party Rep. Kang Sun-young.

Lt. Gen. Han Ki-sung, former commander of the Army's 1st Corps, who was relieved of duty in August over a controversial guideline ordering front line crew-served weapons to be kept unloaded, also appeared as a witness.

“There were no restrictions on warning shots or other live-fire responses [because of the unloaded weapons],” Han said, adding that he made the decision after consulting his staff. JCS Chairman Gen. Jin Yong-seung disagreed.

“There was a problem, and I ordered it corrected,” Jin said.

BY LEE YU-JUNG, SHIM SEOK-YONG [[email protected]]