North Korean soldiers briefly crossed the Demilitarized Zone (DMZ) into South Korean territory earlier this week but retreated after South Korean forces fired warning shots, South Korea’s military said on June 11.

The Korean Demilitarized Zone is a heavily armed strip of land running across the Korean Peninsula near the 38th parallel north. The DMZ is 248km long and 4km wide. / Newsis

North Korean soldiers working inside the DMZ crossed the Military Demarcation Line (MDL) separating the two Koreas in the central section of the border at around 12:30 a.m. on June 9, according to the Joint Chiefs of Staff.

These soldiers immediately retreated north after warning broadcasts and warning shots from the South Korean military. “We are closely monitoring the movements of the North Korean troops and taking necessary measures,” the military said.

Lee Sung-joon, the Joint Chiefs of Staff spokesperson, said the military concluded that the soldiers did not appear to have intentionally crossed the MDL, considering the site is a heavily wooded area where MDL signs are not clearly visible, and as they immediately moved north following the warning broadcasts and shots.

The military stated that many of the North Korean soldiers were carrying construction tools and some were armed, suggesting they were simply on their way to work. The exact number of North Korean soldiers who crossed the MDL and the number of warning shots fired by South Korean forces were not disclosed.

The day before the soldiers crossed the MDL marked the first time in nearly six years that South Korea resumed anti-Pyongyang propaganda loudspeaker broadcasts in response to the North’s campaign of sending trash-filled balloons to the South.