A Christian missionary who was himself detained in North Korea has called for prayers over the 'outrage' and 'tragedy' of the death of the American student Otto Warmbier.

Kenneth Bae, who was held in North Korea from 2012-2014, also called on the secretive dictatorship to release the three Americans still detained there.

Bae, who ran a company specialising in tours of North Korea, was accused by Pyongyang of plotting to bring down the government through religious activities. In April 2013, he was sentenced to 15 years of hard labour, but was released in November 2014 with the help of Barack Obama's administration.

Last night, following the death of the 22-year-old student, Bae said: 'I grieve for the family of Otto Warmbier. This is a young man who had so much promise. He was a college student on a journey to see the world. For North Korea to detain him and sentence him to 15 years in prison was an injustice. But for Otto to be returned to the US in the state he was in – and then for him to die because of it – is not only an outrage, but it is a tragedy for his entire family.

'I cannot understand what the Warmbier family is feeling right now. But I mourn with them, and I pray for them. No words can ease this pain, but we can pray for them. It's my hope and prayer that they also know others in America are mourning with them and will not forget their son and brother.

'As we grieve Otto's passing, I also want people to know that other Americans remain detained in North Korea right now. There are three Americans – Kim Dong Chul, Tony Kim, Kim Hak-Song – and the Canadian pastor Hyeon Soo Lim. But there are certainly many other people living without freedom in the country of 24 million people – enduring horrible circumstances and forced labor – and we do not even know their names.

'We plead with the US government, the international community, and leadership in North Korea to value human lives. Every life is important — Otto's life, lives of the American detainees, and the lives of each person in North Korea. I am a Christian, and part of what that means is to act justly and to have mercy on the innocent. Although we don't know everything about life in North Korea, this much is sure: innocent people like Otto are suffering. I pray that these innocent people suffering in North Korea are not forgotten in this high-stakes game of weapons, sanctions, and international diplomacy.

'Please join me in prayer and be a voice for the innocent. Please join me in praying for Otto's family. This did not have to happen and should never happen again.'

Warmbier died just days after being returned to the US from North Korea in a comatose state.

Warmbier's death on Monday was confirmed by his parents Fred and Cindy Warmbier. In a statement, they blamed his death on the treatment he had received at the hands of North Korea, where he had spent the last 17 months in prison for trying to remove a propoganda poster from his hotel.

After arriving back in the US, it was revealed that the University of Virginia student had suffered extensive brain loss and was unable to communicate.

North Korean authorities blamed his condition on botulism and said they had freed him on 'humanitarian grounds'. His family and US doctors refused to accept the official explanation from North Korea for his deterioration.

'The awful torturous mistreatment our son received at the hands of North Koreans ensured that no other outcome was possible beyond the sad one we experienced today,' Fred and Cindy Warmbier said in a statement.

'When Otto returned to Cincinnati late on June 13, he was unable to speak, unable to see or react to verbal commands. According to the BBC, he had been in a coma for a year.

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

'We thank everyone around the world who has kept him and our family in their thoughts and prayers. We are at peace and at home too,' they said.

Warmbier was in Pyongyang on a tourist trip with other students from the University of Virginia when he was arrested on January 2, 2016, for trying to steal a propoganda poster from a hotel and sentenced to 15 years of hard labour.

According to the BBC, Warmbier had confessed to trying to take the propaganda poster as a 'trophy' for a US church.

The US President Donald Trump responded to his death in a statement condemning 'the brutality of the North Korean regime as we mourn its latest victim.'

His local church had responded to news of his condition by praying for him and his family. Eric Miller, pastor of the Ascension and Holy Trinity Church in Cincinnati, said of Cindy and Fred Warmbier: 'I can't even begin to put myself in their shoes. [Otto's] imprisonment has touched people's lives in our church setting. It touches a lot of people in our community in a variety of ways.'