Kim Hak Song upon return to the United States last month.

One of the American citizens who was released by North Korea and returned to the United States last month, was told by his captors he was detained because of the “hostile act” of prayer.

Kim Hak Song was arrested on a train from North Korea’s capital Pyongyang to China in May last year for allegedly having committed hostile acts against the North Korean regime.

He told his home church, the Oriental Mission Church in East Hollywood, Los Angeles, on Saturday 2 June that when he asked the authorities what he had done wrong, the answer was that he committed the crime of prayer, reported Religion News.

Officials had records of an email he had sent to his church asking them to pray for the people of North Korea, and they knew about the fact that he had led morning prayers for a worship group, he said.

Kim Hak Song had been visiting North Korea for a month at a time from China, where he worked as a missionary for his church. In North Korea he was involved with agricultural development work with the Pyongyang University of Science and Technology.

Although he was not tortured during his imprisonment, his wife said he still “felt the pain and struggle” and was dealing with the trauma, according to Religion News.

Song was released on 9 May with two others, Kim Dong-chul, a pastor in his early 60s, and Tony Kim (also known as Kim Sang-duk). According to the White House it was a gesture of goodwill ahead of the meeting between US President Donald Trump and the North Korean leader Kim Jong-un scheduled for 12 June.

Kim Hak Song said he was unaware of the negotiations for his release and only realised he was free when he boarded the US government aircraft.

Meanwhile 300 rights groups have written a letter to North Korea’s leader, urging him to make “lasting improvements to the dire human rights situation” in the country, to convince the rest of the world “that he is serious about change”, said Benedict Rogers, East Asia Team Leader with Christian Solidarity Worldwide, one of the signatories of the letter.

“It is essential that the human rights crisis in North Korea, which the UN Commission of Inquiry described as ‘without parallel’ and as amounting to crimes against humanity, is addressed as part of engagement with the North Korean regime,” Rogers said.

According to the US State Department’s International Religious Freedom Report for 2017 there were more than 1,300 religious freedom violations in North Korea, while it is estimated that its camps hold more than 120,000 political prisoners.

The country is number 1 on the 2018 Open Doors World Watch List of the 50 countries where it is most difficult to live as a Christian.