By Charles Scanlon
BBC News, Seoul
South Korea has opened immigration checkpoints at the demilitarised zone which has sealed it off from North Korea for more than half a century.
The facilities will ease the journey of hundreds of South Koreans who commute each day to a new industrial zone on the northern side of the line.
South Korea said the two sides were in the process of becoming a unified community.
The highway north from Seoul used to stop dead at the world's last cold war frontier - a tangle of barbed wire, minefields and tank traps focused on the 4km-wide demilitarised zone (DMZ).
But now, about 400 South Koreans commute each day on recently-built roads through the line.
The new immigration facilities will help speed up the process and give some of the atmosphere of a normal border crossing.
The South's unification minister said growing contacts would show the Koreans could build peace and prosperity on their own.
Contact, however, is still carefully controlled by North Korean officials anxious to restrict outside influences.
The South Koreans are confined to a fenced-off industrial zone on the outskirts of the city of Kaesong just a few kilometres north of the border.
Six thousand North Koreans are currently employed at Southern-owned factories, which are attracted by the cheap labour.
Southern workers travel in convoy each day following a military vehicle which is replaced by a North Korean jeep midway through the buffer zone. They drive past the rusting remains of a steam train stranded in no-man's land since the Korean war of the 1950s.
South Korea is pushing ahead with investment in the zone despite the North's pursuit of nuclear weapons.
There are plans to employ more than half a million North Koreans within six years, but officials say success will depend on a diplomatic breakthrough and more support from the United States.