Donald Trump has said he believes Kim Jong-un over claims he knew nothing about the “really bad things” that happened to Otto Warmbier, an American who suffered severe brain damage while detained in North Korea.

The US president was asked about the case in a hastily arranged press conference following a summit in Vietnam which was cut short on Thursday after the two leaders failed to find agreement over limiting North Korea’s nuclear ambitions.

Warmbier, a US college student, was imprisoned by Pyongyang in 2016 after being convicted of the theft of a propaganda poster. The US government secured his release the following year, but he died days after arriving back on American soil in a coma.

“I really don’t think it was in his interests at all,” Mr Trump told reporters, referring to Mr Kim, who has been described by the president as a “friend” and a “great leader”.

Taking credit for the return of three US hostages from North Korea in May last year, Mr Trump continued: “What happened is horrible, I really believe something very bad happened to him and I don’t think that the top leadership knew about it, and when they had to send him home – by the way I got the prisoners back, I got the hostages back, and Otto was one of the hostages, but Otto came back in a shape that was not even to be talked about.

Trump and Kim: leaders arrive in Vietnam for talks Show all 7 1 /7 Trump and Kim: leaders arrive in Vietnam for talks Trump and Kim: leaders arrive in Vietnam for talks Donald Trump and Vietnamese President Nguyen Phu Trong make their way to a meeting at the Presidential Palace in Hanoi Reuters Trump and Kim: leaders arrive in Vietnam for talks Donald Trump waves a Vietnamese flag as Vietnam's Prime Minister Nguyen Xuan Phuc looks on AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks Donald Trump waves as he leaves the Presidential Palace in Hanoi AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks North Korean leader Kim Jong-un, right, is welcomed on his arrival at the Melia Hotel in Hanoi AP Trump and Kim: leaders arrive in Vietnam for talks Kim Jong-un waves as he arrives by train in the Vietnamese border town of Dong Dang AP Trump and Kim: leaders arrive in Vietnam for talks North Korean leader Kim Jong-un receiving a situation report before the summit with Trump AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks The motorcade carrying U.S President Donald Trump drives past Ho Chi Minh Mausoleum AP

“I find it … I thought it was horrible. Now the others came back extremely healthy, but Otto came back in a condition that was just terrible, and I did speak about it, and I don’t believe that he would have allowed that to happen, just wasn’t to his advantage to allow that to happen.

“Those prisons are rough, they’re rough places, and bad things happened, but I really don’t believe that he was … I don’t believe he knew about it.”

Warmbier returned to the US in June 2017 in a vegetative state, which, according to North Korean officials, he went into after contracting botulism shortly after his conviction more than a year earlier.

Doctors said Warmbier likely suffered a cardiac arrest, which led to brain damage, but were unable to work out the cause. They said there was no definitive evidence of torture.

Asked if Mr Kim told him directly he was unaware of Warmbier’s plight, Mr Trump said: “He felt badly about it. I did speak to him, he felt very badly.

“He knew the case very well, but he knew it later and you’ve got a lot of people – big country – a lot of people, and in those prisons and those camps you have a lot of people, and some really bad things happened to Otto, some really, really bad things, but he tells me that he didn’t know about it, and I will take him at his word.”

'Sometimes you have to walk' President Trump addresses media as talks with Kim Jong Un break down with no deal

Mr Trump’s defence of Mr Kim echoed his defence of other autocratic rulers, including most infamously his siding with Vladimir Putin over his own US intelligence community. Mr Trump said he believed the Russian leader’s claims of innocence over Russia’s hacking of the 2016 US election.

Saudi Arabia’s de facto ruler Mohammed bin Salman also received support from Mr Trump in the wake of the murder of journalist Jamal Khashoggi.