Unification Minister Chung Dong-young says North Korean defectors are sneaking back to their communist homeland to check on family members remaining in the North.

At a meeting with reporters on Thursday, Chung said some Northern defectors in the South are currently under surveillance or being slapped with unspecified punishment for re-entering North Korea to visit family members left behind in the Stalinist state.

The minister's comments come in the wake of Seoul's revelation Thursday that it was detaining a North Korean who had reportedly confessed to carrying out espionage activities following his apparent defection to South Korea.

Chung also said about 40 defectors from North Korea are currently staying overseas longer than scheduled.