Warmbier was arrested by North Korean authorities in January 2016 for attempting to steal a propaganda poster from a restricted area within his hotel.
President Donald Trump today denounced North Korea as "a brutal regime" after the death of a 22-year-old USA student released by the reclusive country in a coma last week.
Otto Warmbier, 22, died at 2:20 p.m. (1820 GMT) surrounded by his family, his parents said in a statement released by the University of Cincinnati Medical Center.
It said the student had been "unable to speak, unable to see and unable to react to verbal commands".
"There has still been nearly no information disclosed about his period in detention", the company said in its statement. He died six days later in his home town of Cincinnati, Ohio, with US President Donald Trump blaming Pyongyang's "brutal regime" for his plight. Warmbier was in detention in North Korea for almost a year and a half.
Secretary of State Rex Tillerson said in a statement that the USA holds North Korea "accountable" for Warmbier's imprisonment, and demanded Pyongyang free three other Americans, all of them of Korean ancestry, now being held there. His family said it was told he had been a coma since soon after his March 2016 sentencing.
The death is likely to exacerbate relations between the United States and North Korea, whose leader, Kim Jong-un, has threatened to attack the USA with nuclear weapons in recent months. Doctors said he returned with severe brain damage, but it wasn't clear what caused it. Parents Fred and Cindy Warmbier told The Associated Press in a statement the day of his release that they wanted "the world to know how we and our son have been brutalized and terrorized by the pariah regime " and expressed relief he had been returned to "finally be with people who love him".
Dr. Daniel Kanter, the director of neurocritical care for the University of Cincinnati Health system described Warmbier's state as one of "unresponsive wakefulness".
"In the final year of his life, he lived the nightmare in which the North Korean people have been trapped for 70 years: forced labour, mass starvation, systematic cruelty, torture and murder". The American student was sentenced to 15 years of hard labor.
In a statement, the Warmbier family thanked the medical team that treated his son and those who had offered their thoughts and prayers.
"We have been struggling to process the result", Young Pioneer Tours, the China-based travel agency that had taken Warmbier to the North, said in a Facebook post. "The U.S. government should not just throw up its hands and say, 'This is just how North Korea is.' But how do you do that in a smart way where there is some modicum of accountability?"
Fred Warmbier praised his son's "performance" and Mr Trump's administration.
On Monday, the family paid tribute to Warmbier in their emotional statement.
"North Korea sent him back to the United States before he died because more questions would have been raised about his death and the situation would have gotten worse if it had returned his dead body", said Cheong Seong-jang, an analyst at the private Sejong Institute in South Korea.
"There was a lull, followed by the appearance of two North Korean security officials, who took Warmbier to a private room".
Tensions between the United States and North Korea have been heightened by dozens of North Korean missile launches and two nuclear bomb tests since the beginning of past year.