USA student Otto Warmbier freed by North Korea has 'severe brain injury'

The father of Otto Warmbier, the U.S. student released from North Korean detention this week, lashed out Thursday at the reclusive regime, saying he did not believe its explanation for how his son fell into a coma.

The 22-year-old was taken to University of Cincinnati Medical Center, where doctors say he is in a coma but in stable condition.

Warmbier experienced extensive tissue loss in all regions of the brain, doctors said, but he showed no signs of physical trauma and medical tests offered no conclusive evidence as to the cause of his neurological injuries.

North Korea reportedly told a US official that Otto contracted botulism while detained and slipped intothe coma after taking a sleeping pill. Warmbier made it clear he does not believe North Korea's explanation of botulism combined with a sleeping pill for Otto's condition.

AP also said that "doctors treating him in the USA said they found no evidence of botulism, but did find severe brain damage consistent with losing oxygen to the brain".

"There is no reason for any civilized nation to keep his condition secret and deny him medical treatment for so long", Fred Warmbier said at a press conference in Cincinnati.

The Warmbiers were told just a week ago that their son contracted botulism and fell into a coma shortly after being arrested and sentenced, in March previous year. They said they wanted all to know they and their son had been "brutalised and terrorised by the pariah regime".

He was medically evacuated from North Korea and arrived in Cincinnati late Tuesday.

Warmbier, 22, a University of Virginia student from suburban Cincinnati, was medically evacuated to the USA on Wednesday.

US officials wouldn't say if Yun met with other North Korean diplomats while in the country or conducted more extensive diplomacy.

At a news conference earlier on Thursday, father Fred Warmbier said they are left with many questions and no answers.

The Washington Post also condemned the North for its "horrendous mistreatment" of Warmbier and urged the United States to step up sanctions on the Kim Jong-un regime. They said there is evidence Warmbier suffered a respiratory arrest, which led to a lack of oxygen to the brain.

Warmbier's father, Fred, verbally lashed North Korea, describing it as a "pariah regime" that had "brutalized and terrorized" his son, the New York Times reported.

Fred Warmbier expressed gratitude for the United States administration's efforts in his son's favour, and said he spoke personally with President Donald Trump late Wednesday night.

There had been speculation as to whether Warmbier's release had anything to do with basketball star Dennis Rodman's recent trip to North Korea.

Gratton also said he had no clue that Warmbier had taken the sign from the hotel lobby. However, Rodman reportedly said the issue was "not my goal right now".

The U.S. government accuses North Korea of using such detainees as political pawns.

A Department of State spokeswoman won't say what envoy Joseph Yun gleaned about the medical conditions of the other Americans.

North Korea is believed to operate political prison camps and foreign nationals have also been detained on political grounds, Ojea Quintana said.