South Korea's spy agency has decided to retain 13 North Korean defectors at the heart of a bitter dispute between the rivals, with Pyongyang accusing Seoul of abducting the group from their posts at a restaurant in China, an official said on Tuesday.

"The director of the National Intelligence Service has decided to extend their protection," a South Korean official said, citing a law covering the resettlement of North Korean defectors and concerns for their safety.

"A propaganda campaign by the North" over the status of the group was a factor in the decision, the government official told Reuters, requesting anonymity because the topic is sensitive.

North Korea says the South abducted the 12 waitresses and the restaurant manager and has demanded their return, but the South has said the group decided to defect of its own free will.

The Seoul Central District Court said it had ruled to stay a petition filed by Minbyun, or Lawyers for a Democratic Society, seeking to question the women.

"We don't think it is possible to make a decision without confirming the restaurant workers' intent in this case," Chae Hee-joon, a lawyer for Minbyun, told reporters, adding they had filed a recusal motion to the court, citing the women's absence.

The spy agency has said it will not present the defectors in court and only their legal representatives will attend.

The intelligence agency has held the group since its April 7 arrival in the South at a facility it runs on the southern outskirts of the capital, Seoul, where more than 1,000 defectors from the North stay each year in the initial stages.

For up to 180 days, they are screened and questioned on their lives in the North.

The spy agency's decision means the 13 will not be moved to a resettlement complex where other defectors spend 12 weeks to learn about a vastly different new life in the South.

South Korea is technically at war with the North because their 1950-53 conflict ended in an armistice, not a peace treaty.