BEIJING — North Korea said Friday that the death of American tourist Otto Warmbier was a mystery, denying he had been tortured and casting itself as the “biggest victim” of the affair.

In its first public reaction to Warmbier’s death, a Foreign Ministry spokesman also tried to shift blame onto the administration of former President Obama, blaming it for refusing to have a dialogue with Pyongyang and claiming it had never officially asked for his release.

“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 American University student was arrested while visiting North Korea as a tourist, accused of stealing a propaganda poster and sentenced to 15 years hard labor. He was returned to the United States last week suffering brain damage and died Monday.

North Korea said the sentence had been appropriate and called speculation that he had 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 had slipped into a coma after suffering from 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 saying it appeared he had suffered severe neurological damage, possibly as a result of cardiopulmonary arrest.

Friday’s statement appeared to support that possibility, saying that North Korean doctors had “brought him back alive whose 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.”