The US-led United Nations Command assessed that a North Korean mine found south of the Military Demarcation Line had been deliberately placed there and installed more than 12 months ago, South Korea's Joint Chiefs of Staff said Monday.
This came as Army Lt. Gen. Kwon Dae-won, vice chair of the JCS, confirmed that North Korean-made land mines were the cause of the Sept. 21 explosions in the Demilitarized Zone that injured three South Korean military personnel, and demanded North Korea's apology to South Korea.
"The mine had been deliberately placed there and that it had been installed more than 12 months ago," Kwon said, adding the UNC's assessment led to the same conclusion.
Kwon said the assessment was made during a joint on-site investigation conducted by the South Korean military and the UNC from Sept. 26-29.
The military also concluded that the mines had been planted rather than washed into the area, citing their locations and spacing as well as the condition in which they were found.
The JCS said the mines were confirmed to be North Korean resin-cased antipersonnel mines through forensic analysis by the National Forensic Service. The military also assessed that at least four mines had been planted in the area.
The two blast sites and a separate mine found during the investigation were located about 10 meters south of the MDL, according to the JCS.
The military removed the North Korean minefield at around 12:51 p.m. Monday, in coordination with the UNC.
Kwon said the operation was aimed at removing mines placed south of the MDL in violation of the Armistice Agreement and protecting South Korean troops operating in the DMZ.
"If North Korea does not voluntarily remove the minefields it has installed south of the MDL, our military will continue mine-clearing operations for the peace of the Demilitarized Zone and the safety of our troops," Kwon said.
The JCS also urged North Korea to apologize for the injuries and immediately remove mines it has placed south of the MDL.
"We strongly urge North Korea to offer a sincere apology to our service members injured in the mine explosions and to immediately remove the mines it installed in violation of the Armistice Agreement," Kwon said.
A military official said the operation marked the first physical removal of a North Korean minefield found south of the MDL.
North Korea was notified in advance of the operation through UNC channels, while the South Korean military issued warning broadcasts shortly before carrying it out, military officials said.
Separately, Brig. Gen. Kim Seong-yun, the JCS' director of intelligence analysis, said North Korea has significantly expanded work near the MDL as part of what Pyongyang calls border fortification. North Korea has deployed as many as 7,000 personnel a day this year for mine-laying, fence construction and tactical road work, Kim said.
The military estimates that work to clear vegetation near the MDL is nearing completion, while minefields, fences and tactical roads are about 40 to 60 percent complete, with the overall work expected to be completed within two years.
Kim said North Korean troops have crossed the MDL around 50 times this year, up from 17 such cases in 2025 and nine in 2024.
Most of this year's crossings have been concentrated in a specific eastern-sector area, where North Korean troops have repeatedly used a patrol route extending about 10 meters south of the MDL, resulting in more than 40 crossings at a single location, he said.
Kim also said South Korea and the UNC are working to reconcile differences over the precise location of the MDL.
South Korea currently uses an MDL marked on military maps established by the US National Geospatial-Intelligence Agency in 2004, while the UNC uses coordinates generated through its 2016 MDL project. The line connecting the remaining MDL markers also does not fully coincide with either, Kim said.
Of the 1,292 markers installed following the 1953 Armistice Agreement, only about 200 remain identifiable, according to the JCS.
Kim said the military continues to respond under established procedures, issuing repeated warning broadcasts when North Korean troops approach the MDL, with additional warning broadcasts and warning shots when they cross it.
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