The warning came from the head of the North Korean forces stationed in the frontier village of Panmunjom -- where the ceasefire agreement to end fighting in the 1950-53 Korean War was signed.
Panmunjom has hosted multiple inter-Korean talks over the decades and is heavily guarded, with mostly South Korean and US troops on the southern side under the auspices of the UN Command (UNC).
The North Korean military official, who was not named, said recent activities by US troops threatened to destabilise the sensitive area.
Given the military sensitivity of Panmunjom, where North and South Korean border guards stand almost eyeball-to-eyeball, the official said such activity was particularly dangerous.
"The slightest accidental mistake or undesirable behaviour could lead to a catastrophic military clash," he said.
North Korea regularly denounces the US troop presence in the South, but it is unusual for it to focus on activities in Panmunjom -- one of the few avenues of cross-border communication.
The North Korean official cited other "sinister" activity by US troops, including messages relayed across the border by loudspeaker and letters with "dishonest contents" that were left in huts straddling the border.
Such actions had multiplied since US President Barack Obama visited South Korea in April, he said.
