Writing on Twitter, the US President said 22 year old Otto Warmbier from Ohio was "tortured beyond belief" during his time in detention.
His words on Tuesday came as the United States imposed further sanctions on Pyongyang, this time targeting eight banks and dozens of finance bosses. Relations between the two countries have deteriorated in recent weeks.
The rhetoric contradicts North Korean officials who claimed they had been the target of a smear campaign by the US.
They insist cruel treatment and torture played no part in the death of Otto Warmbier. The University of Virginia student passed away on 19th June, days after his release from North Korea on humanitarian grounds.
Warmbier spent more than a year in detention after being sentenced for 15 years behind bars for allegedly trying to steal a propaganda poster from a hotel to take to his church.
Doctors in the US claimed Mr Warmbier - who arrived back in his country in a coma - had suffered severe neurological injury from unknown cause.
His relatives believe torture was used, however North Korea insists it followed its domestic laws and international standards in dealing with him.