WASHINGTON • US President Donald Trump has accused North Korea of brutally abusing an American student who had been held captive in North Korea, saying the young man had been "tortured beyond belief".

His remarks came after the parents of Mr Otto Warmbier, 22, who died in June a few days after he was sent home in a mysterious coma, lashed out at Pyongyang in their first interview since his death, Agence France-Presse (AFP) reported.

They said he was blind and deaf, had mangled teeth, and was jerking violently on a stretcher with a feeding tube coming out of his nose.

Mr Trump had previously blamed Pyongyang's "brutal regime" for Mr Warmbier's plight, but it was the first time that he publicly accused North Korea of torture in the case, reported AFP.

"Otto was tortured beyond belief by North Korea," Mr Trump said on Twitter yesterday, following the airing of an interview with Mr Warmbier's parents.

Mr Warmbier was arrested in January last year at the end of a brief tourist visit to the isolated country. The University of Virginia student was convicted of offences against the state for trying to steal a propaganda poster from a Pyongyang hotel and sentenced to 15 years of hard labour.

"They kidnapped Otto, they tortured him, they intentionally injured him. They are not victims, they are terrorists," Mr Warmbier's father Fred said yesterday on the Fox & Friends news show.

He had previously criticised former president Barack Obama's administration for how little it did for his son, saying officials counselled the family against speaking out to avoid antagonising the North Korean regime, said AFP.

Mrs Cindy Warmbier told Fox & Friends that she and her husband had been informed that their son was brain damaged. She said: "So what we pictured, because we are 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 would get the best care and love, that he would come out of it."

But his injuries were much worse than what they had imagined. "We walked over to the plane... When we got halfway up the steps, we heard this howling, involuntary, inhuman sound," Mr Fred Warmbier told Fox. They then saw Otto on a stretcher, making the scary cries and jerking in a violent manner.

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

North Korea has denied it cruelly treated or tortured him.