The incursion across the border separating the two armies took place in an overgrown area of the heavily fortified border zone and was likely accidental, the Joint Chiefs of Staff said.
South Korean troops fired warning shots after North Korean soldiers briefly crossed the border this week, Seoul's military said, quoted by AFP.
Relations between the two Koreas - formally still at war as the 1950-1953 conflict ended in an armistice rather than a peace treaty - are at one of their lowest points in years.
"Some North Korean soldiers operating in the Central Front Demilitarized Zone briefly crossed the Military Demarcation Line (MDL)," the SCS said in a statement, referring to the Line of Control between the two Koreas.
"After our military fired warning shots, they retreated to the north," the statement said. Subsequently, "no unusual movements" were observed.
The entry was likely accidental, said Joint Chiefs of Staff spokesman Lee Sung-jun.
"The situation at that time was that the demilitarized zone was already overgrown with trees and the VDL marking was not clearly visible. There was no road and (the North Korean soldiers) were moving through the bushes, and we observed (them) even before they approached the VDL." , Li said.
"We believe that they did not intend to invade, given that immediately after the warning broadcasts and warning shots, they moved north," he added.
In recent weeks, North Korea has sent more than a thousand balloons loaded with garbage such as cigarette butts and toilet paper to the South in response to anti-Pyongyang propaganda balloons sent to the North by activists.
In response, the South Korean government ended a 2018 military agreement to reduce tensions and resumed propaganda broadcasts along the border, angering the North, which warned Seoul it was creating a "new crisis".
North Korea may also reinstall its loudspeakers along the border, Seoul's military said, a tactic it has used since the 1960s, usually broadcasting praise of the ruling Kim family. They suspended the campaign in 2018 when relations briefly warmed.
In recent months, the North has also been seen removing street lights from the few roads that once connected the two Koreas, as well as destroying sections of the inter-Korean railway line, Yonhap news agency reported. | BGNES
