"The fact that Warmbier died suddenly in less than a week after his return to the U.S. in his normal state of health indicators is a mystery to us as well," the spokesman was quoted as saying by the official Korean Central News Agency. "To make it clear, we are the biggest victim of this incident."
The 22-year-old University of Virginia student was arrested while visiting North Korea as a tourist, accused of stealing a propaganda poster and sentenced to 15 years in prison with hard labor. He was returned to the United States last week with brain damage and died Monday.
North Korea said the sentence was appropriate and called speculation that he died as a result of beating or torture "groundless."
"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 humanitarian basis until his return to the U.S., considering that his health got worse," the spokesman said.
North Korea said Warmbier slipped into a coma after contracting botulism and taking a sleeping pill. But officials at the University of Cincinnati Medical Center, where Warmbier was treated after his return, said they had found no trace of the disease. Instead, they saidit appeared he had suffered severe neurological damage, possibly as a result of cardiopulmonary arrest.
Pyongyang's statement Friday appeared to support that possibility, saying that North Korean doctors had "brought him back alive" after his "heart had nearly stopped."
The North Korean statement said the country was a victim of a "smear campaign" by the United States as a part of a "frantic effort" to impose "heinous sanctions," the NK News website reported.
"Why the U.S. government which claims to care about the welfare of its citizens had not even once made an official request for the release of Warmbier on humanitarian basis during the Obama administration?" the statement said. "The answer should be given by the U.S. itself."
Earlier this week, Obama spokesman Ned Price said the previous administration "had no higher priority than securing the release of Americans detained overseas." He added that its efforts to secure Warmbier's release had "never ceased, even in the waning days of the administration."