WASHINGTON - Otto Warmbier, a US college student who was released by the Democratic People's Republic of Korea (DPRK) less than a week ago, died on Monday, his parents said.

"It is our sad duty to report that our son, Otto Warmbier, has completed his journey home. Surrounded by his loving family, Otto died today at 2:20 pm (1820 GMT)," his parents Fred and Cindy Warmbier said in a statement.

Warmbier's parents thanked the "wonderful professionals" at the University of Cincinnati Medical Center and denounced the DPRK for mistreating their son.

Warmbier's parents have told US media that he was medically evacuated from the DPRK in a coma.

The DPRK confirmed his release in a report by the state-run Korean Central News Agency, saying he was sent back home "on humanitarian grounds".

The 22-year-old student from the University of Virginia had been in a coma for more than a year after contracting botulism soon after he was sentenced to 15 years of hard labor in a trial by the DPRK Supreme Court on March 16, 2016, according to US local media.

Doctors in Cincinnati had described Warmbier's condition as a state of "unresponsive wakefulness" and said he suffered a "severe neurological injury" of unknown cause. They said they found no active sign of botulism or evidence of beatings.

Warmbier was detained by DPRK authorities at the Pyongyang International Airport on his way back home in January 2016 after he attempted to take a political slogan sign from a staff-only area in a hotel where he stayed during his tour to the country.

Xinhua