North and South Korea trade warnings after landmine discovery in DMZ

United Nations Command determined that North Korea violated the 73-year-old Korean War armistice after investigators found a North Korean anti-personnel mine buried on the southern side of the Demilitarized Zone, the command said Wednesday.

The mine was discovered the previous day near where two landmines exploded on Sept. 21, injuring South Korean soldiers, according to the command and the South Korean military.

U.N. Command and the South Korean military began investigating the blast site on Sunday. The overall probe into the explosions remains underway, and the command’s armistice finding applies only to the mine found on Tuesday.

The command is “addressing the violation through established Armistice mechanisms,” spokeswoman In-kyeong Yun said by email Wednesday. She did not immediately respond to a follow-up message seeking details about those mechanisms.

North Korea denied responsibility for the incident Wednesday and accused the South of making groundless allegations.

Kim Yo Jong, sister of North Korean leader Kim Jong Un, accused South Korea’s “armed gangsters” of using the incident to justify political and military provocations against the North, according to a statement in the state-run Korean Central News Agency.

She also warned that North Korea would launch “immediate and merciless” retaliatory attacks if South Korean forces fire on North Korean troops working along the border.

South Korea, meanwhile, demanded that the North stop its border fortification work and apologize.

“North Korea must immediately halt activities that heighten tensions on the Korean Peninsula, such as the so-called border fortification,” Lt. Gen. Kang Hyun-woo, chief director of operations for South Korea’s Joint Chiefs of Staff, said during a Wednesday press briefing.

“North Korea bears full responsibility for any situation that may arise in the future,” he said, according to a transcript.

Pyongyang has spent the past two years fortifying its side of the DMZ, including building fences and laying mines.

South Korea’s military said Monday that preliminary evidence indicated that the two mines that exploded on Sept. 21 also likely belonged to North Korea.

The mines detonated as members of South Korea’s 25th Infantry Division cleared a new search route for an investigation of terrain changes near the Military Demarcation Line. The soldiers were near an area where South Korea found evidence in September 2025 that North Korean troops may have planted mines.

Forensic analysis of equipment worn by the injured soldiers found substances consistent with material used in North Korean mines, Joint Chiefs Vice Chairman Lt. Gen. Kwon Dae-won said Monday.

South Korea’s military also has no record of laying mines at the blast site, he said.

Four mines, including the two that exploded, have now been discovered in the area.

South Korean Defense Minister Kang Shin-chul said Tuesday that investigators believe it is unlikely the mines were carried into the area by flooding.

South Korean officials warned in July that heavy monsoon rains could wash mines from areas near the border into the South.

However, the mine found Tuesday was buried rather than washed into place, Kang told the National Defense Committee. The two mines that exploded were about 6 ½ feet apart, and all four were found within a small area, leaving “little possibility” they had been swept there by rain, he said.