Six South Koreans were released from concentration camps in North Korea last Friday and returned home, but all now face criminal charges here.
One returned with the ashes of his wife, whom he had strangled in what appears to have been a botched double suicide.
Prosecutors on Sunday applied for arrest warrants for the six on charges of violating the national security law since they had gone to North Korea without authorization.
The six had apparently been persuaded by propaganda that they would have a better life in North Korea. They illegally entered the North by crossing the Apnok or Duman rivers or jumping off Chinese sightseeing boats to swim across the North Korea-China border.
Most of them went because their business here failed or they had some kind of personal trouble. Prosecutors quoted them as testifying they believed they would be taken better care of in the North.
Some had already taken part in pro-North Korean campaigns on the Internet before they left.
But instead of being welcomed with open arms they were interned in prison camps in Onsong and Hoeryong in North Hamgyong Province, Sinuiju in North Pyongan Province, and Wonsan in Kangwon Province, where they were questioned for between 14 and 45 months.
On Friday afternoon, the six returned through the truce village of Panmunjom. Identified only by their surnames Chung (43), Hwang (56), Kim (44), Lee (65), Song (27) and Yoon (67), they were immediately subjected to more questioning by South Korean authorities.
The North's official KCNA news agency said Pyongyang "leniently pardoned" them on humanitarian grounds and decided to send them back to reunite with their families, because they "candidly admitted and repented their crime" of illegal entry.
Some pundits here believe they were released because North Korea wants to create a friendlier climate for cross-border talks.