Otto Warmbier's parents have revealed for the first time the horrific state he was in when he returned from North Korea after being tortured into a coma.

They say their 22-year-old son was blind, deaf and had mangled teeth when they first laid eyes on him after he was brought back to the US following his brutal 18 months imprisonment at the hands of Kim Jong Un's regime.

Fred and Cindy Warmbier told Fox News on Tuesday that they heard a 'howling' sound when they walked up the steps of the private medical plane carrying their son after it landed in Cincinnati, Ohio back on June 13.

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Fred and Cindy Warmbier have revealed the horrific state their 22-year-old son Otto was in when he returned from North Korea after being tortured into a coma

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'We walked over to the plane, the engines are still humming, they had just landed…when we got halfway up the steps we heard this howling, involuntary, inhuman sound. We weren't really certain what it was,' Fred said.

They quickly realized it was their son Otto as they saw him screaming and jerking violently on a stretcher. Fred said Otto's mother and sister ran off the plane at the initial sight of him.

'Otto had a shaved head, he had a feeding tube coming out of his nose, he was staring blankly into space, jerking violently,' Fred said.

North Korea is not a victim. They're terrorists. They kidnapped Otto. They tortured him. They intentionally injured him. Fred Warmbier

'He was blind. He was deaf. As we looked at him and tried to comfort him it looked like someone had taken a pair of pliers and rearranged his bottom teeth.'

He said within two days of being home, Otto's fever spiked to 104 degrees and he had a large scar on his right foot.

Cindy said they had only been told that their son had suffered brain damaged when it was revealed the North Korean regime was returning Otto to his family on 'humanitarian release'.

They said the reality of his injuries were much more severe than they could ever have imagined.

'We thought he was in a coma. You couldn't call it a coma,' she said.

Heart wrenching images showed Otto's limp body being carried off a private medical plane after it landed Cincinnati, Ohio back on June 13. Tubes were clearly visible on his face

North Korean officials claimed that Otto (above in February 2016 in North Korea) had contracted botulism - a form of food poisoning - a day after he was jailed and that is what caused his medical decline

'What we pictured, because we're optimists, is that Otto would be asleep and maybe in a medically induced coma and then when our doctors here would work with him and he'd get the best care and love that he would come out of it.

'Our image of Otto, as you know, was of someone just wonderful, beautiful inside and out. And to see how he came home was too much for us.

'I almost passed out but I got it together and I rode in the ambulance with him. I did not want him to be alone anymore. He'd been alone for way too long. We stayed with him and loved him as best as we could.'

His parents said Otto spent his final days jerking and moaning in the tortured state before he died at the University of Cincinnati Medical Center on June 19.

He was blind. He was deaf. As we looked at him and tried to comfort him it looked like someone had taken a pair of pliers and rearranged his bottom teeth Fred Warmbier

The University of Virginia student was sentenced in March 2016 to 15 years hard labour in North Korea after he was accused of stealing a propaganda poster from the hotel where he had been staying during a brief tourist visit.

North Korean officials claimed that Otto had contracted botulism - a form of food poisoning - a day after he was jailed. They claimed that a sleeping pill they gave him sent him into a coma.

The American doctors who reviewed MRI scans that were sent back on a private medical plane with him say they saw no evidence of botulism. They did say he had suffered extensive brain loss.

The Warmbiers said they have had some time to heal in the three months since they buried their son but decided to speak out after seeing North Korea try to victimize themselves.

Their interview comes amid an escalating war of words between the Trump administration and North Korea. A North Korean official has claimed President Donald Trump has, in effect, declared war, which the White House denied.

In March 2016, Otto was led away by North Korean police after being sentenced to 15 years hard labour. North Korean officials say the following day, he contracted botulism - a form of food poisoning - and that this is what caused his medical decline

Otto's family held a public funeral for him at his old high school in the town of Wyoming, Ohio

'We see North Korea claiming to be a victim and that the world is picking on them and we're here to tell you: North Korea is not a victim. They're terrorists,' Fred said.

'They kidnapped Otto. They tortured him. They intentionally injured him. They are not victims.'

Cindy said she felt Otto had only been sent home because the North Koreans knew he was about to die.

Otto's parents reiterated their belief that North Korea should be listed as a state sponsor of terror.

Fred has previously criticized former president Barack Obama's administration for how little it did for their son, saying officials had counseled the family against speaking out to avoid antagonizing the North Korean regime.

President Donald Trump tweeted shortly after the Warmbier's interview aired, saying: 'Great interview on @foxandfriends with the parents of Otto Warmbier: 1994 - 2017. Otto was tortured beyond belief by North Korea.'

Trump had previously blamed North Korea's 'brutal regime' for Warmbier's plight but it was the first time the president publicly accused North Korea of torture in the case.

US officials have said Trump was personally taken aback by Warmbier's death and his comment Tuesday ratchets up the pressure on Kim Jong-Un's regime.