North Korean troops build a road near the DMZ in this undated photo provided by South Korea's Joint Chiefs of Staff on June 18, 2024.

North Korean troops build a road near the DMZ in this undated photo provided by South Korea's Joint Chiefs of Staff on June 18, 2024. (South Korea Joint Chiefs of Staff)

CAMP HUMPHREYS, South Korea — North Korean soldiers briefly crossed the border with South Korea early Tuesday, prompting the South’s military to fire warning shots for the second time this month, according to the South Korea Joint Chiefs of Staff.

Twenty to 30 North Korean soldiers working in the Demilitarized Zone crossed the Military Demarcation Line, the border between the two countries, around 8:30 a.m., the Joint Chiefs said in a text message to media outlets Tuesday.

South Korea’s military fired warning shots and made loudspeaker broadcasts to warn the North’s forces of their intrusion, according to the Joint Chiefs. The North Koreans retreated to their side of the border following the warnings, the Joint Chiefs added.

The incident marks the second border crossing by North Korean troops this month; about 20 soldiers were detected by the South on June 9. The 150-mile-long, 2½-mile-wide DMZ contains thick foliage that sometimes obscures signs indicating each sides’ territory, according to the South’s military. 

The location of Tuesday’s crossing was in an area apart from the earlier incident, the South’s military said. 

In a separate news release Tuesday, the Joint Chiefs said North Korean soldiers working in the DMZ were injured in recent months after they triggered multiple landmines.

A “large number” of Korean forces have been laying mines, reinforcing roads and doing other military work in the border separating the two Koreas since April, according to the Joint Chiefs.

The Joint Chiefs said the North was possibly fortifying its southern border as a measure to prevent its citizens from defecting to the South. The Joint Chiefs added that it expected North Korean forces to “gradually expand” their work along the border.

“The South Korean military is closely tracking the North Korean military’s activities on the frontlines … and is working closely with the [U.N. Command],” the release said.

The U.N. Command is the multinational military body responsible for upholding the armistice between North and South Korea.

North Korea’s border operation comes amid renewed tensions on the Korean Peninsula. 

On June 4, South Korea formally suspended the Comprehensive Military Agreement, which was designed to lower military tensions by prohibiting drills and establishing no-fly zones near the DMZ. 

North Korea had already withdrawn from the 2018 agreement seven months earlier, citing the South’s decision to partially suspend the accords. Seoul had suspended a provision that banned aerial reconnaissance operations after Pyongyang successfully launched a reconnaissance satellite on Nov. 21.

North Korean leader Kim Jong Un is scheduled to meet Russian President Vladimir Putin in Pyongyang on Tuesday, the first such trip in 24 years, according to the state-run Korean Central News Agency.

South Korea’s Foreign Affairs Ministry said Putin’s visit should not lead to a closer military relationship that results in further violations of U.N. Security Council resolutions, according to a ministry news release Friday.

The United States and its allies have accused North Korea of violating Security Council resolutions that prohibit the communist regime from conducting ballistic missile tests since 2016.

David Choi is based in South Korea and reports on the U.S. military and foreign policy. He served in the U.S. Army and California Army National Guard. He graduated from the University of California, Los Angeles.

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