North Korea, a Prison without Bars

In North Korea, the Constitution provides for "freedom of religious belief"; the Democratic People's Republic of Korea is an atheist state. North Korea is officially an atheist state, and government policy continues to interfere with the individual's ability to choose and to manifest his or her religious belief. The regime continues to repress the religious activities of unauthorized religious groups. The government deals harshly with all opponents, including those who engage in religious practices deemed unacceptable by the regime. An estimated 150,000 to 200,000 persons were believed to be held in political prison camps (Kwalliso) in remote areas, many for religious and political reasons. North Korea sees organised religious activity as a potential challenge to the leadership.

(http://www.nationalreview.com/articles/345474/north-korea-prison-without-bars-nina-shea)