Firecrackers and white balloons filled the skies near the border as a five-car train started rolling north on a restored track on the west side of the peninsula. On the eastern side, a North Korean train crossed into the South on another reconnected rail line where it was greeted by children bearing flowers.

It was the first train crossing of the 2.5-mile-wide no man's land dividing the two sides since inter-Korean rail links were cut off early in the 1950-53 Korean War.

The trial run was the latest symbol of a historic reconciliation that the longtime foes began pursuing with the first-ever summit of their leaders in 2000. That summit has led to a series of exchange projects, including the opening of cross-border roads that thousands of South Koreans cross each year as tourists, or to work in special enclaves in the North.

The detente has often stalled, mainly because of tensions over North Korea's nuclear programmes.

Thursday's one-time test run came after repeated delays since the rail lines were linked in 2003.

"It is not simply a test run. It means reconnecting the severed bloodline of our people. It means that the heart of the Korean peninsula is beating again," Unification Minister Lee Jae-joung said at a ceremony at Munsan station, about 8 miles south of the Demilitarised Zone, before boarding the train.