South Korea has sent trains across the world’s most heavily militarised border into North Korea for the first time in a decade. It’s part of a mission to eventually modernise the North’s dilapidated network and connect it with the South.

Six rail cars carrying dozens of South Korean officials and engineers will inspect 1,200km (745 miles) of track over 18 days, according to the South’s unification ministry.

The survey required special permission from the United Nations to take prohibited goods into the North, which remains under heavy economic sanctions over its nuclear weapons program.

Trump angry after South Korea signals it may ease North Korea sanctions Read more

South Korean officials will use the study to draw up plans for modernising the North’s ageing rail lines, most of which date from the early 20th century.

The six rail cars making the journey contain living quarters, office space and storage for fuel and generators. They will travel from the border along the length of North Korea to its border with China, along two lines running near the west and east coasts.

Facebook Twitter Pinterest A South Korea train prepares to travel across the border into North Korea. Photograph: Pool/Getty Images

The difference between the rail networks in the North and South is striking, with trains on the North’s decrepit network often moving at a snail’s pace, compared with the South’s high-speed lines. Modernising the North’s lines to bring them up to international standards could take years or decades and would require billions of dollars in investment.

The North Korean leader, Kim Jong-un, admitted his country’s trains were in an “embarrassing” state in his first meeting with South Korean president, Moon Jae-in, in April. One line was previously connected over a short distance in 2007, but the last time trains ran across the border was in 2008 when a South Korean cargo train operated five times a week. Services were halted after worsening relations with Pyongyang.

Moon has been eager to push ahead with closer economic links with the North despite the United States insisting on progress in denuclearisation talks, which have been stalled for months. An earlier attempt by Seoul to conduct the rail survey was stopped by the US-led United Nations command, which controls the border.

South Korea intends to hold a ribbon-cutting ceremony opening two rail links with the North by the end of the year, according to the South’s Yonhap news, but the move will be almost entirely symbolic as long a sanctions remain in place, preventing most goods from crossing the border.