AN AMERICAN student sentenced to 15 years of hard labour in North Korea has been medically evacuated from the rogue nation in a coma — a state he has been in for more than a year.

Otto Warmbier, 23, was due to arrive home in Cincinnati, in the US state of Ohio, overnight, having been evacuated through a US military base in Sapporo, Japan.

Mr Warmbier’s parents, Fred and Cindy, told The Washington Post their son has been in a coma since shortly after his trial in Pyongyang in March 2016 — his last public appearance.

The Warmbiers were told that he contracted botulism soon after his trial and was given a sleeping pill, from which he never woke up, according to The Washington Post.

“Our son is coming home,” Fred Warmbier said. “At the moment, we’re just treating this like he’s been in an accident. We get to see our son Otto tonight.”

But they later told Associated Press in a statement: “We want the world to know how we and our son have been brutalised and terrorised by the pariah regime (in North Korea).”

A senior US official said there had been intelligence reports in recent weeks that Mr Warmbier had been repeatedly beaten while in custody, the New York Times reported.

The official, who was not authorised to discuss intelligence and spoke anonymously, said there also had been concerns that he had died as a result of the beatings.

However the Times reported Mr Warmbier was in fact alive, and his release “followed an extraordinary period of clandestine negotiations between American and North Korean officials in Oslo, Norway and New York”.

Secretary of State Rex Tillerson announced Mr Warmbier’s release on Tuesday morning, but did not discuss the student’s medical condition.

“At the direction of the President, the Department of State has secured the release of Otto Warmbier from North Korea,” he said in a statement. “Mr Warmbier is en route to the US where he will be reunited with his family.”

Secretary Tillerson informed President Donald Trump by phone, with an anonymous senior administration official telling The Washington Post the president’s last instruction was: “Take care of Otto.”

Mr Warmbier, a University of Virginia undergraduate, was convicted and sentenced in a one-hour trial in North Korea’s Supreme Court. The US government condemned the sentence and accused North Korea of using such American detainees as political pawns.

The North Korean court held that Mr Warmbier had committed a crime “pursuant to the US government’s hostile policy toward (the North), in a bid to impair the unity of its people after entering it as a tourist.”

Before his trial, Mr Warmbier had said he tried to steal a propaganda banner as a trophy for an acquaintance who wanted to hang it in the Friendship United Methodist Church. That would be grounds in North Korea for a subversion charge.

North Korea announced Mr Warmbier’s arrest in late January 2016, saying he committed an anti-state crime with “the tacit connivance of the US government and under its manipulation.”

Mr Warmbier had been staying at the Yanggakdo International Hotel. It is common for sections of tourist hotels to be reserved for North Korean staff and off-limits to foreigners.

In a tearful statement made before his trial, Mr Warmbier told a gathering of reporters in Pyongyang he was offered a used car worth $US10,000 ($13,200) if he could get a propaganda banner and was also told that if he was detained and didn’t return, $US200,000 ($265,000) would be paid to his mother in the form of a charitable donation.

Mr Warmbier said he accepted the offer because his family was “suffering from very severe financial difficulties.”

Mr Warmbier also said he had been encouraged by the university’s Z Society, which he said he was trying to join. The magazine of the university’s alumni association describes the Z Society as a “semi-secret ring society” founded in 1892 that conducts philanthropy, puts on honorary dinners and grants academic awards.

The announcement comes as former NBA player Dennis Rodman paid a return visit to the rogue nation.

It was not immediately clear if Rodman’s visit was purely coincidental with Mr Warmbier’s release.

Rodman has travelled to the isolated nation four times previously and is one of few people to have met both North Korean leader Kim Jong-un and President Trump. Speaking to reporters in Beijing before his arrival in Pyongyang on Tuesday, he said that the issue of several Americans detained by North Korea is “not my purpose right now.

Secretary Tillerson also said in his statement on Tuesday the State Department was still discussing three other detained Americans with North Korea.