A United Nations human rights investigator has called on North Korea to explain why an American student was in a coma when he was returned home this week after more than a year in detention there.
Otto Warmbier, 22, has a severe brain injury and is in a state of "unresponsive wakefulness", his Ohio doctors said.
His family said he had been in a coma since March 2016, shortly after he was sentenced to 15 years' hard labour in North Korea.
"While I welcome the news of Mr Warmbier's release, I am very concerned about his condition, and the authorities have to provide a clear explanation about what made him slip into a coma," Tomas Ojea Quintana, the UN special rapporteur on human rights in the Democratic People's Republic of Korea (DPRK), said in a statement issued in Geneva.
Warmbier, from a Cincinatti suburb, was arrested for trying to steal an item bearing a propaganda slogan, North Korean media reported. On Thursday, North Korea said that it had released him "on humanitarian grounds".
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The University of Virginia student's father, Fred Warmbier, said his son had been "brutalised and terrorised" by the North Korean government.
Fred Warmbier said the family did not believe North Korea's story that his son had fallen into a coma after contracting botulism and being given a sleeping pill.
Ojea Quintana called on North Korea to "clarify the causes and circumstances" of Otto Warmbier's release.
"His case serves as a reminder of the disastrous implications of the lack of access to adequate medical treatment for prisoners in the DPRK," he said.
