North and South Korean soldiers have made several friendly crossings into each other's territory for the first time since the countries were divided.
The men were checking the dismantling of guard posts in the Demilitarised Zone (DMZ) along the border as part of the two sides' recent rapprochement.
Footage showed the soldiers shaking hands at the border before crossing.
The Korean War in the 1950s left the peninsula divided and no formal peace treaty has ever been signed.
As part of the talks between the divided peninsula, the South's President Moon Jae-in and the North's Kim Jong-un agreed to remove some of the guard posts on the heavily fortified border.
The two leaders held a historic meeting in April, which led to talk between North Korea and the US.
Since November, both North and South have blown up or dismantled 10 of their border posts.
On Wednesday, South Korean inspectors visited each of the guard posts on the North's side while North Korean inspectors later inspected the same process in the South.
"This marks the first time since the division that the soldiers of the North and South... are peacefully crossing the military demarcation line," the South Korean defence ministry said in a statement.
Both sides still have more guard posts in the DMZ, both over and underground.
There has been speculation Mr Kim could visit Seoul this year but the South's government earlier this week said that no such trip was expected before 2019.
Despite its misleading name, the DMZ is one of the world's most heavily fortified places.
The area is a strip of land 250km (155 miles) long and 4km (2.5 miles) wide that runs across the peninsula.
It is heavily mined and fortified with barbed wire, rows of surveillance cameras and electric fencing - and is guarded by tens of thousands of troops on both sides.