President Donald Trump has condemned North Korea’s “brutal regime” after the death of American student Otto Warmbier who had been jailed there for more than 15 months.

North Korea returned the 22-year-old student to the US last week, saying he had been in a coma for a year and that it was acting on humanitarian grounds.

Otto Warmbier’s parents said he had been subjected to “awful torturous mistreatment”.

Fred and Cindy Warmbier said in a statement that their son had died at 14:20 local time on June 19 at the Cincinnati hospital where he had been receiving treatment.

They said he had “completed his journey home”.

Fred and Cindy Warmbier wrote: “When Otto returned to Cincinnati late on June 13, he was unable to speak, unable to see and unable to react to verbal commands.

“He looked very uncomfortable – almost anguished. Although we would never hear his voice again, within a day, the countenance of his face changed – he was at peace. He was home, and we believe he could sense that.”

They also said: “The awful torturous mistreatment our son received at the hands of the North Koreans ensured that no other outcome was possible beyond the sad one we experienced today.”

Otto Warmbier, who was jailed in North Korea for trying to steal a propaganda sign from a hotel, did not regain consciousness.

President Trump said that a “lot of bad things happened” to Otto Warmbier, but added: “At least we got him home to be with his parents, where they were so happy to see him, even though he was in very tough condition.”

The president said Otto Warmbier’s death had deepened his administration’s resolve “to prevent such tragedies from befalling innocent people at the hands of regimes that do not respect the rule of law or basic human decency”.

“The United States once again condemns the brutality of the North Korean regime as we mourn its latest victim.”

The company Otto Warmbier traveled with, Chinese company Young Pioneer Tours, has announced it will no longer take visitors from the US to North Korea.

North Korea said Otto Warmbier had contracted botulism, a rare illness that causes paralysis, soon after his trial in March 2016. He was given a sleeping pill and had been in a coma ever since.

However, a team of doctors assessing Otto Warmbier in Cincinnati said they had found “no sign of botulism”.

Otto Warmbier had suffered a “severe neurological injury” of unknown cause, the doctors said, leading to an extensive loss of brain tissue.

He could open his eyes but showed no sign of response to communication.

Doctors said the most likely cause, given Otto Warmbier’s young age, was cardiopulmonary arrest that had cut the blood supply to the brain.

It is not known when Otto Warmbier had fallen into his coma and there is a suspicion it was quite recently, as the US was only told at the beginning of this month about his health situation.

The North Koreans may have realized there was the possibility of an American citizen dying on their hands.

Former New Mexico Governor Bill Richardson, who has helped free other Americans in North Korea, said he had met North Korean envoys 20 times during Otto Warmbier’s incarceration and on no occasion was his health mentioned.

Bill Richardson called for the release of the three US citizens still held in North Korea:

• Kim Dong-chul, a 62-year-old naturalized US citizen born in South Korea, who was sentenced to ten years hard labor in April 2016 for spying;
• Korean-American professor Kim Sang-duk (known as Tony Kim), who was detained in April 2017. The reasons for his arrest are not yet clear;
• Kim Hak-song, like Kim Sang-duk, worked at the Pyongyang University of Science and Technology (PUST) and was detained in May 2017 on suspicion of “hostile acts” against the state.

President Donald Trump was criticized in May when he said he would be “honored” to meet North Korean leader Kim Jong-un at the “appropriate” time.