'No excuse' for N.Korea's treatment of US student: father

The father of Otto Warmbier, the US student released from North Korean detention in a coma, says there is "no excuse" for the way his son was treated.

According to the hospital treating him, the 22-year-old suffered severe neurological injury during more than a year of detention in the isolated country, for stealing a political poster from a hotel.

"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," Fred Warmbier told a news conference in the family's home city of Cincinnati, Ohio.

"I call on them to release the other Americans being held," he urged.

Fred and Cindy Warmbier have said their son was "terrorized and brutalized" by Kim Jong-Un's regime.

According to Kelly Martin, spokeswoman for the UC Health University of Cincinnati medical centre, "Otto is in stable condition but has suffered a severe neurological injury."

The team treating him were to deliver a full medical update later in the day.