A South Korean missionary has been sentenced to life in a North Korean prison for attempting to organize underground churches.

On Friday, Kim Jung-wook admitted to committing anti-North Korean religious acts and "malignantly hurting the dignity" of the country's supreme leadership, or the ruling Kim family, The Associated Press reported quoting state media.

Now, the missionary will be subject to hard labor for life due to charges of spying and trying to set up underground churches.

An unidentified North Korean defense attorney said Kim Jung-wook "sincerely repented of his crimes and apologized for them" and urged that the court commute the death sentence demanded by prosecutors, who produced "evidence such as religious books, memory cards, sex CDs and spying devices carried by the accused for criminal purposes."

Jung-wook worked out of Dandong, China, where he helped North Korean defectors flee to South Korea through other countries including Thailand and Laos, according to a friend. However, Chinese authorities caught 12 North Korean women in August 2012 from his shelter and sent them back to North Korea. According to reports, Jung-wook was crossing into North Korea in December to find out about the women and to learn about a food shortage there, but got caught by authorities.

According to International Christian Concern, North Korea has been identified as the worst persecutor of Christians. To counter international criticism, the North Korean government publicly blames Christian missionaries reaching North Koreans "indoctrinate the illegal border crossers with anti-DPRK ideology and send them back to the DPRK with assignments of subversion, destruction, human trafficking and even terrorist acts."

Christians caught possessing Christian literature, conducting Bible studies or gathering for prayer meetings are subject to imprisonment - and so are their entire families, including children and elderly grandparents.

There are at least 100,000 Christians in that nation's harsh prison camps, where prisoners face torture, forced labor and possible execution, Christian groups say.

"Christians are the target of fierce government action, and once caught, are not regarded as human," said a veteran observer of North Korea who cannot be identified for security purposes.

North Korea is ruled by the Korea Worker's Party, led by the Kims. The brutal dictatorship has been in place since its formation in 1948.