Story highlights Myunghee Bae says seeing son at a Pyongyang hospital was a "very happy moment"

She was granted a five-day visa to North Korea and three short visits with Kenneth Bae

He was sentenced in May to 15 years of hard labor after being found guilty of "hostile acts"

"Please give him mercy and give him amnesty to send him home," mother asks government

Walking into a Pyongyang hospital room to greet her imprisoned son, Myunghee Bae was overcome with emotion. Talking exclusively to CNN, Bae said it was a "very happy moment. At the same time, I could not believe he was a prisoner in North Korea; a new realization."

Bae was granted a five-day visa to North Korea and three short visits with her son, Kenneth; a total of six hours, in which she says there was not one moment's silence. "He said he's being treated very fairly," she said. "He was taken to a special labor camp, so he was the only prisoner, and a whole lot of people have to stay with him, guards and doctors."

Kenneth Bae, an American citizen, was arrested in November of last year and sentenced in May to 15 years of hard labor . The North Korean regime says he was found guilty of "hostile acts" and attempts to topple the government. His mother says he has a profound love for the country and its people, and any offense he caused was not intentional.

"Always, he wanted to help the people over there, help the country," she said. "He always thought that way, but apparently he misunderstood their system, so a lot of things he realized -- he did some harm to their country." Bae added that her son's Christian faith was so strong, he wanted to convey his feelings. North Korea is officially an atheist state and has punished missionaries in the past.

Although Bae was unable to meet with North Korean officials to plead her son's case, she wants to make her message to them clear: "Please give him mercy and give him amnesty to send him home. We apologize as a family on his behalf, but his health cannot sustain any longer if he is sent back to the labor camp again."

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Bae was forced to work in the camp for three months until his health deteriorated. His mother says his illnesses include diabetes, an enlarged heart, gallstones, back and neck pains, and high cholesterol. Bae says he looked better when she met him than he appeared in the footage of his hospitalization in August. But that brings its own concerns.

"My worst fear is to send him back to the labor camp because his health seems a little bit improved, that's my worst fear. Because I don't think his body can endure eight hours labor a day, six days a week."

Previous Americans detained in North Korea have been released when high-profile visitors have traveled to the country to plead their case. Most notably, former Presidents Bill Clinton and Jimmy Carter went on two separate occasions in 2010. Bae believes her son's case has not encouraged such attention, as relations between Washington and Pyongyang hit a new low this year.

Myunghee Bae says it has been an agonizing 11 months, not only for her, but also for Kenneth Bae's wife and three children. "They all had a very hard time, and I think we all as a family felt helpless. We could not do anything for him, only sending letters ... we don't have any power to bring him home."

The most heart-breaking part of the trip for Bae was leaving Pyongyang and walking out of the hospital without her son. "It was very hard; I cannot express my pain and my heartache to leave him behind as a prisoner in North Korea. How long will it take to see him again?"