North Korea on Thursday unveiled video footage in which the parents of one North Korean restaurant worker who defected to South Korea early this month blamed Seoul for abducting their daughter.

North Korea has claimed that South Korea kidnapped a group of 13 North Koreans who used to work at a North Korea-run restaurant in China. It notified the South last week that it will send their family members to Seoul for a face-to-face meeting.

A group of North Koreans -- one male manager and 12 female employees -- who worked at a restaurant in the Chinese eastern port city of Ningbo defected to South Korea en masse in early April amid toughened international sanctions.

North Korea's main propaganda outlet Uriminzokkiri TV disclosed the footage in which the parents of a female worker condemned Seoul for what they called abducting their loved one, calling for repatriation.

"When we heard our daughter had been kidnapped by South Korea, we could not let go of our deep grief," they were quoted as saying by Uriminzokkiri TV. "We believe that your repatriation will be made."

The footage also contained their utterances of condemnation against President Park Geun-hye.

North Korea has threatened to take strong action against South Korea if Seoul does not accept its demand for the family arrangement and repatriation.

South Korea's unification ministry refused the North's request, saying that the restaurant workers' mass defection was completely of their own free will.

North Korea's committee handling inter-Korean affairs repeated its demand on Thursday that Seoul should return them back home, warning that it will mercilessly counteract if the South fails to do so.

South Korea should "unconditionally and immediately send back the innocent abductees," the Committee for the Peaceful Reunification of Korea said in a statement.

It claimed that as South Korea produced "new divided families" through allurement and abduction, it should not even think of bringing up the issue of reunions of families separated by the 1950-53 Korean War.

As of end-March, the number of North Koreans who defected to the South came in at more than 29,000, with some 1,280 people arriving in the South last year.

North Korea labels defections as abductions by South Korea in a long-running inter-Korean ideological rivalry. The two Koreas are still technically at war since the 1950-53 Korean conflict ended in a truce, not a peace treaty. (Yonhap)