Kim Jong-un has signalled his readiness to allow inspectors into the dismantled Punggye-ri nuclear test site, but Open Doors USA is urging North Korea's Supreme Leader to go further. 

The organisation, which advocates for persecuted Christians worldwide, said the communist country's moves towards denuclearisation were a 'step in the right direction' but voiced concern that 'little has been said' in talks between the US and North Korea about the country's decades-long 'severe human rights violations'. 

It wants North Korea to allow the Red Cross and United Nations Council of Inquiry in to inspect the camps, which it says are 'as bad - or even worse - than Auschwitz'. 

According to Open Doors USA, there are 250,000 North Koreans imprisoned in the camps, including 50,000 prisoners of faith. 

'We must gain transparency into how these people are being treated,' says Open Doors CEO David Curry. 'And then President Trump must make it clear that Kim Jong Un can only be invited back into the world's good graces, and be lauded for political gestures if he commits to resolving decades of human rights violations at the hands of his regime.'

Following a meeting between Kim and US Secretary of State Mike Pompeo in Pyongyang on Sunday, South Korean President Moon Jae-in said a second summit meeting between North Korea and the US was being planned for 'as early as possible'.

President Moon also revealed that Kim was open to a visit from Pope Francis, a surprising announcement given North Korea's poor track record on religious freedom and the fact that it currently has no formal diplomatic ties with the Vatican.

Open Doors USA questioned the invitation, saying, 'How can a dictator who uses the fear of Nazi-style prison camps to rule his people sincerely extend a visit to the Pope?

North Korea has come under fire over prison conditions after missionary Kenneth Bae was sentenced to 15 years of hard labour in 2013.  He revealed how he was frequently hospitalized as a result of the harsh conditions in the prison camp.  After diplomatic efforts by the US, he was freed in 2014.

Last year, the death of Otto Warmbier after 17 months in detention in North Korea caused international outcry.  Warmbier, a 22-year-old student, died days after being returned to the US brain-damaged and in a coma.  North Korean officials said botulism was to blame. 

Open Doors USA said: 'Otto's death serves as a disturbing reflection of Kim's disregard for human life and human rights that continues to characterise and define the communist country.'

The organisation is calling on the world's Christians to join in prayer for the suffering church in North Korea and an end to human rights abuses there. 

'The thought of 50,000 North Korean believers imprisoned for their faith being freed from the gates of these camps and their inhumane living conditions should drive the world's 2.2 billion Christians to their knees,' it said.

'We have a biblical responsibility to intercede for these believers and ask God to make it clear to our leaders that the time is now—for such a time as this—to start this unprecedented freedom work for His suffering people.'