WASHINGTON • American university student Otto Warmbier, who was released by North Korea this week after falling into a coma while in a labour camp, has suffered "severe neurological injury", a hospital spokesman said yesterday.

The 22-year-old from Cincinnati spent 17 months in detention after he was arrested for stealing a political poster from a hotel.

"Otto is in stable condition but has suffered a severe neurological injury," Ms Kelly Martin, spokeswoman for the UC Health University of Cincinnati Medical Centre, said at a news conference at Mr Warmbier's high school in Wyoming, Ohio.

His father, Mr Fred Warmbier said at the news conference his son was "brutalised and terrorised" by the North Korean regime.

He added that the family did not believe North Korea's story that their son had fallen into a coma after contracting botulism and being given a sleeping pill.

"We don't believe anything they (North Korea) say," the elder Mr Warmbier said.

"There's no excuse for the way the North Koreans treated our son and no excuse for the way they have treated so many others. I call on them to release the other Americans being held," he urged.

The student was sentenced in March last year to 15 years of hard labour.

He arrived on a military airplane in his home town late on Tuesday.

North Korea later said it had released him "on humanitarian grounds", state media reported.

But the New York Times quoted a senior United States official as saying that Washington had recently received intelligence reports that Mr Warmbier had been repeatedly beaten in custody.

The release came amid tension between Washington and Pyongyang following a series of missile tests by the North, focusing attention on an arms build-up that Pentagon chief Jim Mattis on Monday dubbed "a clear and present danger to all".

AGENCE FRANCE-PRESSE, REUTERS