North Korea rejected South Korea's claim that North Korean landmines likely caused two Sept. 21 explosions inside the Demilitarized Zone that injured three South Korean soldiers, accusing Seoul of fabricating the findings to justify political and military provocation.
Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, said in a statement carried by state media KCNA that South Korea was "cooking up" what she called groundless allegations.
One of the three South Korean soldiers injured in the explosions lost a foot.
South Korea said its investigation concluded that North Korean resin anti-personnel mines deliberately placed south of the Military Demarcation Line were highly likely to have caused the blasts.
South Korean Defense Minister Kang Shin-chul called the incident a "clear violation of the armistice agreement" and said Seoul would take corresponding measures.
Lt. Gen. Kang Hyun-woo of the Joint Chiefs of Staff demanded that North Korea apologize, take "responsible measures," and immediately halt its border-hardening activities.
"We make it explicitly clear that North Korea bears full responsibility for any future consequences that may arise," he said.
Kim denied that North Korean soldiers had crossed the border and accused South Korean forces of threatening troops working along the frontier with warning broadcasts and shots.
"If the ROK military gangsters fire at our soldiers carrying on the permanent project for the southern border, not warning shots, our border units will take immediate and merciless retaliate attack," she said.
The DMZ has divided the Korean Peninsula since the 1953 armistice and remains one of the world's most heavily fortified and mined borders.
South and North Korea technically remain at war because the Korean War ended with an armistice rather than a peace treaty.