About 28,500 U.S. troops are stationed in South Korea as a deterrent against North Korea -- a legacy of the 1950-53 Korean War that ended in a truce. Border security, however, has been almost entirely undertaken by South Korean forces since a few years ago.

According to the KCNA, a group of U.S. soldiers recently came within 20 meters of the military demarcation line with women, taking photos and throwing bottles of alcohol toward North Korean troops.

"If the South ignores our warning and allows U.S. invasion forces to act rampantly near the military demarcation line, it shall bear the responsibility for all consequences, including human damage," the KCNA said, quoting the message delivered to the South.

The military demarcation line, one of the world's most heavily guarded borders, runs inside of the Demilitarized Zone, a four-kilometer-wide swath of land bisecting the peninsula. Both were established at the end of the Korean War.

North Korea has been increasing its threats against South Korean and U.S. troops involved in border security in recent years, a move analysts believe is aimed at raising tension as the communist state pushes to unite its regime and raise its stakes in negotiations.

(Yonhap News)