Freed Aussie missionary John Short shared his grueling experience after being detained in North Korea.

In a statement obtained by the Australian Associated Press, Short recounted Biblical scriptures that made him to carry on despite the "long and gruelling investigation" during his detention in North Korea.

"There were two-hour sessions each morning, which were repeated again in the afternoon," Short said.

Even with his old age of 75, Short loves exercising. His detention in Pyongyang with constant guard supervision took a toll physically.

"This I found to be most painful physically as an active senior person," he said. "I missed my freedom to walk very much."

During his arrest on Feb 18, he said he had come clean about distributing Christian pamphlets. But he was compelled to admit his crime word-for-word as written in his indictment that he distributed Bible tracts with the goal of making North Koreans become Christians.

He was then informed that he is facing 15 years in prison for his crime. Hence, he agreed on penning his apology to North Korea.

Short was finally deported on Monday following his apology.

Arriving on a flight from North Korea to Beijing, he cried immediately when approached by the press.

He told the media he was really exhausted and looking forward to rest immediately.

According to North Korea's KCNA news agency, North Korea showed generosity when it decided to deport Short due to old age and a signed confession and apology.

He was seen in pictures writing down his apology and affixing his thumb in red ink to the document. He also read out his written apology.

"I realize that my actions are an indelible hostile act against the independent right and laws of the (North). I request forgiveness... and am willing to bow down on my knees. I now realise the seriousness of my insult to the Korean people ... and for this I truly apologise,'' Short read.

His statement also included a disclaimer that U.S. and other western media had maligned North Korea with ''inaccurate and wrong'' reports saying the country is shrouded with religious oppression.