North Korea has issued its first comments on the death of U.S. college student Otto Warmbier, who had been held by Pyongyang for more than a year before his June 13 release, calling the 22-year-old's passing "a mystery" and labeling themselves as "the biggest victim of this incident."

Warmbier's family announced his death Monday, with his father blaming it on the "awful, torturous mistreatment ... at the hands of the North Koreans." The onetime University of Virginia student, who was released in a coma, was freed on "humanitarian grounds," the North said earlier.

In a statement carried Friday by the state-run Korean Central News Agency, a North Korean Foreign Ministry spokesman denied that Pyongyang had tortured or beaten Warmbier, saying that it was the victim of a "smear campaign" and that U.S. doctors could attest to their claims.