Pyongyang says it has been the target of a smear campaign by the United States and South Korea. It claimed North Korea is the "biggest victim" over the 22 year old's death.
Mr Warmbier was sentenced to 15 years in prison and hard labour after he was accused of trying to steal a propaganda poster from a hotel for his church, during a visit with a China-based holiday tour company.
The Ohio man who attended the University of Virginia died on Monday, days after North Korea released him on humanitarian grounds.
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 followed its domestic laws and international standards in dealing with him.
A spokesman for North Korea's foreign ministry was quoted by the Korean Central News Agency as saying the country cared for Mr Warmbier with "sincerity".
They said: "Although we had no reason at all to show mercy to such a criminal of the enemy state, we provided him with medical treatments and care with all sincerity on a humanitarian basis until his return to the US ... considering that his health got worse."
"The smear campaign against DPRK staged in the US compels us to make firm determination that humanitarianism and benevolence for the enemy are a taboo and we should further sharpen the blade of law."