North Korea says it released an American university student over what it calls humanitarian reasons in its first official comment since he was returned to his home state of Ohio in a coma.

The state-run Korean Central News Agency on Thursday said Otto Warmbier had been sentenced to hard labor but didn't comment on his medical condition.

The 22-year-old Warmbier, a University of Virginia undergraduate, was convicted and sentenced in a one-hour trial in North Korea's Supreme Court in March 2016. He got 15 years in prison with hard labor for subversion after he tearfully confessed that he had tried to steal a propaganda banner.

His father, Fred Warmbier, told Fox News that his son was "terrorized and brutalized" and has been in a coma for more than a year.

"Otto is not in great shape right now," his father, Warmbier, told Fox News’ Tucker Carlson in an exclusive interview Wednesday afternoon from his Cincinnati home. "Otto has been terrorized and brutalized for 18 months by a pariah regime in North Korea."

The elder Warmbier singled out Joseph Yun, the U.S. special envoy on North Korea, as a key player in his son's release as well as Secretary of State Rex Tillerson and President Trump.

"They wanted Otto home," Warmbier said. "Cindy and I believe they made this happen."

Warmbier’s interview will air in full Thursday night on “Tucker Carlson Tonight at 8 p.m. ET.

Doctors at the University of Cincinnati Medical Center are evaluating Warmbier, who was admitted Tuesday night in a coma, according to his family.

The Associated Press contributed to this report