North Korea has punished dozens of its citizens for helping a South Korean Christian missionary with his alleged spying activities in the communist country, a news report said Wednesday.

The missionary, Kim Jong-uk, has been held in the communist state for more than four months since he was arrested on charges of spying for South Korea's state intelligence agency in October.

Last month, Kim confessed to committing anti-state crimes and appealed for mercy during a news conference in Pyongyang covered by the North's state media.

After the press conference, dozens of residents in Pyongyang believed to have been involved in Kim's case disappeared, the Washington-based Radio Free Asia reported, citing an unnamed source in Sinuiju, a northwestern North Korean city bordering China.

RFA raised the possibility that the people may have been taken to a concentration camp as political prisoners, adding that several North Korean officials in charge of managing checkpoints where Kim snuck through were also arrested en masse.

As Kim disclosed during the news conference in detail about how he smuggled himself into the country, the North Korean authority possibly obtained a list of people involved in Kim's case after wrapping up its probe into the case.

Experts say those arrested would face heavy punishments for their involvement in Kim's anti-state crimes.

"Those who helped Kim would probably be shot to death by a firing squad or be taken to a political prison camp, at the very least," said Lee Seok-yeong, editor-in-chief of the Free North Korea Radio, a Seoul-based Internet radio founded by North Korea defectors. (Yonhap)