The parents of the 22-year old American college student freed by North Korea say he is in a coma.

They say that Otto Warmbier is on a Medivac flight on his way home. He had been serving a 15-year prison term with hard labour for alleged anti-state acts.

Fred and Cindy Warmbier said in a statement to the Associated Press that they have been told their son has been in a coma since March 2016, and they had learned of this only one week ago.

They said: "We want the world to know how we and our son have been brutalised and terrorised by the pariah regime" in North Korea.

They also said they are grateful he "will finally be with people who love him".

The State Department announced Warmbier's release earlier Tuesday (13 June) but gave no details on his condition.

Republican Sen. Rob Portman says North Korea should be "universally condemned for its abhorrent behaviour." Democratic Sen. Sherrod Brown of Cleveland said the country's "despicable actions ... must be condemned."

The announcement comes as former NBA player Dennis Rodman is paying a return visit to North Korea.

Warmbier is a University of Virginia student from suburban Cincinnati. He was sentenced in March after a televised tearful public confession to trying to steal a propaganda banner.