Otto, a 21-year-old University of Virginia student, was arrested while visiting the country in January. He was taken into detention for trying to steal an item bearing a propaganda slogan from his hotel in Pyongyang.
"The accused confessed to the serious offense against the DPRK he had committed, pursuant to the U.S. government's hostile policy toward it, in a bid to impair the unity of its people after entering it as a tourist," the state-controlled KCNA news agency reported.
Human Rights Watch condemned the jail term handed down to Otto. Japan's Kyodo news agency published a picture showing the student from Vyoming being led from the courtroom by two uniformed guards, with his head bowed. The American looked in distress.
"North Korea's sentencing of Otto Warmbier to 15 years hard labor for a college-style prank is outrageous and shocking, and should not be permitted to stand," Phil Robertson, deputy director of HRW's Asia division, said.
In the court, Otto's defence attorney said the crime committed by his client was so grave that he would not be able to pay even with his death. He, however, proposed to the court a sentence that is reduced from the prosecution's request of a life sentence,
Last month, Warmbier told reporters during a press meet in Pyongyang that his crime was "very severe and pre-planned."