North Korea appearing to build walls outside DMZ, satellite footage shows

North Korea has begun building an apparent wall near its border with South Korea, according to new satellite footage reported by multiple outlets.

Satellite images from June 17 showed three white structures along the eastern part of the North Korean border, according to a BBC Verify analysis. An area of land inside of the Demilitarized Zone (DMZ) also appeared to be cleared, per BBC.

The 155-mile-long DMZ serves as a buffer zone between North Korea and South Korea, both of which have a series of troops deployed there.

North Korean military members have been performing “unexplained activities” between the DMZ and the military demarcation line, which divides the peninsula, South Korea’s Yonhap News Agency reported, citing an unidentified military source.

The activities included erecting walls, digging the ground and road construction, though it was not clear if these activities indicated an intention to build a long wall or establish defensive structures at certain points, the source told Yonhap.

It comes days after a group of North Korea soldiers, who were doing construction work, crossed the military demarcation line. South Korea broadcast a warning and fired warning shots, prompting the soldiers to retreat.

The Associated Press reported last week North Korea’s construction could be seeking to make it harder for North Korean civilians to move to the south.

Tensions have persisted between the two countries and earlier this month, North Korea sent hundreds of balloons carrying trash into multiple provinces of South Korea, including areas of Seoul.

In response, South Korea played Korean pop music on its loudspeakers and anti-Pyongyang propaganda in what it promised would be an “unbearable” retaliation for the balloons.