He served 18 months of a 15-year prison term in the hermit kingdom for alleged anti-state acts.
Trump was immediately informed and ordered Otto's medical evacuation, with the agreement of the North Koreans, according to people with knowledge of the process.
Yun went on a secret mission to North Korea to bring out Otto Warmbier, the University of Virginia student who was detained in January previous year and had fallen into a coma for reasons that are not yet clear.
The North has occasionally jailed USA citizens and released them only after visits by high-profile political figures, including former president Bill Clinton.
Joseph Yun, U.S. special representative for North Korea policy.
The New York Times reported a senior United States official as saying the authorities recently received intelligence indicating Warmbier was repeatedly beaten while in custody.
After Trump took office as president, the Department of State briefed him on the situation, CNN reported.
"Sadly, he is in a coma and we have been told he has been in that condition since March of 2016", they said. On Monday, they arrived in Pyongyang and Tuesday Warmbier was on a plane back to Cincinnati. An ambulance took Otto Warmbier from the airport to the University of Cincinnati Medical Center.
Warmbier's parents, Fred and Cindy, confirmed their son was on a medevac flight.
University President Teresa Sullivan said in a statement that the school is relieved to hear Warmbier was released, but is concerned about his condition.
The American college student being held captive in North Korea since last January has finally returned home to the U.S. after diplomats learned he's been in a coma for more than a year.
The U.S. government condemned the sentence and accused North Korea of using such American detainees as political pawns.
Tillerson said the State Department is continuing to discuss three other detained Americans with North Korea. The Department of State, on the orders of the president, secured the young man's release, and he returned home Tuesday. He said Warmbier, of Wyoming, in suburban Cincinnati, was en route to the U.S.
Pyongyang assented, and preparations were made to bring Warmbier home.
Much about the hastily arranged release remains a mystery.
The news surfaced after the flamboyant retired NBA basketball star Dennis Rodman - a former contestant on Trump's "Celebrity Apprentice" reality show - flew to Pyongyang to resume his quixotic quest to broker detente between his United States homeland and Kim Jong-Un's authoritarian regime.
The announcement comes as former National Basketball Association player Dennis Rodman is paying a return visit to North Korea. He says in a statement that the State Department secured Warmbier's release at the direction of President Donald Trump. "Overall, it might have been meant to spur diplomacy, but I don't know if that will be the case because of his poor condition".
The statement offered no other details and made no mention of Rodman's visit. Asked later at a Senate committee hearing about Warmbier's health, he declined to comment.
Ultimately, North Korea allowed only one visit, with a different prisoner. "That's outrageous that they didn't notify the USA and that the Swedes have not been given access to him".
An American college student who was released from a North Korean prison is finally home but in a coma and undergoing treatment at an OH hospital.
Apparently the release of Otto Warmbier had nothing to do with Dennis Rodman.
PYONGYANG, North Korea (AP) - Dennis Rodman's visit to North Korea has been uncharacteristically low-key so far. "My hope is that he is used to start dialogue". The onset of his condition was estimated to be shortly after a televised court confession wherein Warmbier claimed "manipulation" by the USA government had urged him to remove the propaganda poster, which is tantamount to the criminal charge of "hostile acts against the DPRK state".