North Korea has demanded Seoul repatriate a dozen waitresses who fled to the South two years ago, just days after abruptly calling off a planned inter-Korean meeting following weeks of tentative rapprochement.
The issue has long been controversial, with Pyongyang claiming the women were kidnapped from a North Korean state-run restaurant in China while Seoul insists they defected of their own free will.
But the restaurant's manager said in a recent interview he had lied to the women and blackmailed them into following him under the orders of the South's spy agency.
The fate of the women could jeopardise relations between the two countries, said a statement from the North's Red Cross carried by the official KCNA news agency late Saturday.
"The South Korean authorities should... send our women citizens to their families without delay and thus show the will to improve North-South ties," the statement said.
At a landmark summit last month in the Demilitarised Zone that divides the peninsula, North Korean leader Kim Jong Un and the South's President Moon Jae-in pledged to pursue denuclearisation and a peace treaty.
A rapid thaw in tensions earlier this year saw Pyongyang release three US detainees and invite foreign media to witness the closing of its nuclear test site ahead of a planned summit between Kim and President Donald Trump in Singpore next month.
But Pyongyang "indefinitely" postponed a high-level meeting with the South last week in protest of joint military exercises between Seoul and Washington and also has threatened to cancel the Singapore summit.