ATLANTA, Georgia (CNN) -- Images from video smuggled from North Korea show a public execution and what appears to be a concentration camp housing political prisoners, according to a CNN documentary set to air Sunday night.In one clip, the residents of a village gather on a hillside to watch the firing-squad execution of a man accused of helping a defector cross into China. North Korean dissidents shot the video, which they smuggled out of the country through a network of contacts into their communist neighbor to the north.The North Korean government did not immediately respond to CNN's request for comment on the documentary's allegations.Human Rights Watch has estimated there are 200,000 political prisoners inside North Korea; Pyongyang denies any camps exist.North Korea is the last Stalinist regime, a closed one-party state founded on a personality cult, a rogue regime known for repression of its people and a menacing nuclear arms program, a nearly bankrupt nation, where, in the 1990s, the U.S. government says more than 2 million people starved to death during a famine. Kim Jong Il denied the famine even existed. Sarah McDonald, who produced and directed the documentary, "Undercover in the Secret State," said her crew interviewed a man who had been in a camp shown in the movie."What he described, we didn't put it in the film," she said Friday from London, England. "It is so appalling, you just can't imagine. He said that 95 percent of people who go into that prison die in the prison. Their whole motivation is to kill these people, but they won't let them die easily."They -- they torture them to death over a very long period of time." Dissidents used new technology like small digital cameras and cell phones to get the images and to set up their escapes to China and safe house in Bangkok, Thailand, the documentary shows. In another scene, a man defaces a poster of Kim Jong Il then flees the country with the image. He tells Korean journalist Jung-Eun Kim he wants the world to know of the growing opposition movement within North Korea. Other images from the film include emaciated children begging and stealing on streets littered with dead bodies and a nearby market selling bags of rice that had been provided by the United Nations for famine relief. "Some of [the dissidents] are motivated because their families actually starved to death in front of them, and they realized that they just had to go out and seek a way of ensuring that their lives were changing in the future," McDonald said. "Others have actually had a sense of the outside by going into China and realizing that life on the outside is not what it appears."