Defectors and analysts have claimed abuse like that inflicted upon US student Otto Warmbier is a routine experience for those in North Korea's concentration camps.
It is thought there are up to 120,000 North Koreans in the camps as well as three Americans, according to Fox News.
Jun Heo, who was sent to prison for defection, told Fox News that he was a teenager when he was sent to a concentration camp in North Korea and it was routine for inmates to be tortured within an inch of their lives.
Heo had travelled to China in order to live there, but the plan unravelled because the man he was staying with in China was a spy.
He said that there would be around 20 people in each tiny cell, although men and women were separated. Despite this, mothers were allowed to stay with young male babies.
Heo also said those imprisoned would be forced to perform hard labour from 6:30am until at least 8pm, and at night he heard the most terrifying screams from other people.
The former prisoner said women were taken in the night to be raped. Others tried to sleep, but were heard moaning in pain as they were starving.
Heo has now defected again to South Korea and is studying English at the Teach North Korean Refugees centre.