The 22-year-old University of Virginia student from Cincinnati had spent more than a year in North Korean detention.
The 22-year-old University of Virginia student from Cincinnati had spent more than a year in North Korean detention after being arrested for stealing a political poster from a hotel. His family have said he was "terrorised and brutalised" by Kim Jong-Un's regime.
"Otto Frederick Warmbier, who had been in hard labour, was sent back home on June 13, 2017 on humanitarian grounds according to the adjudication made on the same day by the Central Court of the DPRK," the state-run Korean Central News Agency said in a one-line statement.
Warmbier's release came after a flurry of secret diplomatic contacts between Washington and Pyongyang, which culminated in Joseph Yun, the State Department's special envoy on North Korea, travelling to Pyongyang to secure Warmbier's release.
"Joseph Yun went to Pyongyang to accompany Mr Warmbier home," Thomas Shannon, undersecretary of state for political affairs, told reporters in Seoul Wednesday.
Warmbier's parents Fred and Cindy have said that they were told their son had been in a coma since March 2016, allegedly after falling ill from botulism and being given a sleeping pill.
"Otto is not in great shape right now," Fred Warmbier told Fox News Wednesday after his son arrived back in the US on a military airplane and was taken straight to the University of Cincinnati Medical Center for urgent treatment.
Warmbier had been sentenced to 15 years of hard labour, a punishment the US decried as far out of proportion to his alleged crime, accusing the North of using him as a political pawn.
The New York Times reported a senior US official as saying the authorities recently received intelligence indicating Warmbier was repeatedly beaten while in custody.
-- Coma likely 'accident' ---
Go Myong-Hyun, researcher at the Asan Institute for Policy Studies, told AFP that it was unlikely North Korea would have intentionally put a detained US citizen -- valuable diplomatic bargaining chips for Pyongyang -- into a coma.
"It must have been an accident and that's probably why they were hiding it for a year," he said.
"If they wanted to get something from the US by torturing Warmbier, they would have live-streamed or at least issued photos of him being tortured," he said, adding the regime was likely "perplexed" by the entire situation.
Three more US citizens are currently being held by North Korea, including two men who taught at a Pyongyang university funded by overseas Christian groups, and a Korean-American pastor who was accused of espionage for the South.
Foreigners who have been detained or imprisoned in North Korea, such as US missionary Kenneth Bae, have later said they endured long hours of strenuous work, health problems, and verbal and emotional abuse by their captors.
Koo Kab-Woo, professor at Seoul's University of North Korean Studies told AFP that Warmbier's release "on humanitarian grounds" did not mean Pyongyang was admitting to any kind of maltreatment or health problems.
"North Korea would have calculated before his release and hoped for a positive effect," on bilateral ties, he said, adding that this could backfire if Warmbier's health condition was more serious than they had anticipated.
"The case is definitely different from previous releases of detainees," which have usually come after a visit from high-profile political figures, including former president Bill Clinton.
The release came amid tension between Washington and Pyongyang following a series of missile tests by the North, focusing attention on an arms buildup that Pentagon chief Jim Mattis on Monday dubbed "a clear and present danger to all."
Washington has stepped up pressure on China and other foreign powers to enforce existing UN sanctions, and has deployed increased military assets of its own in the region.
Warmbier's evacuation coincided with the arrival in Pyongyang of flamboyant retired NBA basketball star Dennis Rodman -- a former contestant on US President Trump's "Celebrity Apprentice" reality show -- but US officials have said Rodman had nothing to do with the release.