Underground railway brings glimmer of hope to the secret Christian 'spies' of North Korea

Smuggled out on tiny scraps of folded paper, the news from North Korea's underground church brings both fear and hope to the Christians in China operating a covert and daring struggle to undermine the North Korean regime.

Smuggled out on tiny scraps of folded paper, the news from North Korea's underground church brings both fear and hope to the Christians in China operating a covert and daring struggle to undermine the North Korean regime.

"Whoever has a Bible in their hands is accused of being a spy – anything connected with the outside world can mean arrest or death," says one note. "We almost starved to death, but you sent food unexpectedly," reads another. "We have unspeakable joy."

A third, with dangerous frankness, says: "We don't know how long this suffering will go on, We have joy in our hearts. Almighty God prepared paradise in heaven for us and this mortal life is short. We are diligently preaching the gospel. We tell people the food comes from Christians around the world. Our numbers are increasing every day."

Some believe there are 500,000 Christians in the North praying secretly in caves or restricted to tiny groups so that under torture they cannot reveal the names of others.

They are backed by a dedicated, some say reckless, minority of South Korean Christians determined to see Christianity unite the two Koreas. They follow the philosophy of the German Lutheran pastor Dietrich Bonhoeffer, who was executed for taking part in a failed plot to kill Hitler.

One of the most daring groups, Durihana, is determined to further an alternative strategy to the sunshine policy of engagement with North Korea promoted by the South Korean President, Kim Dae Jung, who is himself a Presbyterian elder.

Most churches in the South support the policy and seek co-operation with the North's leader, Kim Jong Il, and its official Korean Christian Federation, which claims a membership of 12,000, three functioning churches and a number of house churches.

Those who disagree with the policy are backed by international groups such as Open Doors, founded 45 years ago by Brother Andrew, the Dutch-born author of God's Smuggler. It says that since 1994, Christian missionaries have established 540 underground cells in the North and have smuggled in hundreds of thousands of bibles.

Recently missionaries working in China have found it increasingly difficult to operate. Last year, Chinese police caught the Rev Chun Ki Won of South Korea while he was leading 12 refugees across the Sino-Mongolian border. He was jailed for seven months and mistreated, but freed after a trial and a 50,000 yuan (£3,700) fine.

In April the police caught the Rev Choi Bong Il, who is still in jail and in May, the Rev Joseph Choi, an American citizen, was caught along with 14 of the 38 children he was looking after. Both are members of Durihana. Many other missionaries have disappeared either in North Korea or in China, and their fate has depended on secret negotiations and the payment of large ransoms. Others may have been murdered.

China launched the manhunt three years ago as the frigid relations between the two neighbours warmed before two head of state summits in 2000 and 2001.

Previously China had turned a blind eye both to hundreds of thousands who crossed unofficially into China and to the activities of the missionaries and aid workers who helped them.

An underground railroad enabled some refugees to reach South Korea via third countries such as Russia, Mongolia, Burma or Laos where either the South Korean embassy or the United Nations High Commission for Refugees (UNHCR) could help them.

According to official figures, – thought to be deliberately under-reported – more than 1,200 people defected to South Korea last year, while China allowed more than 130 people who had sneaked into foreign missions to leave for South Korea via the Philippines.

The Chinese offered rewards to informers, closed existing churches and issued local police with arrest quotas. Those caught helping the refugees were fined as much as 30,000 yuan (£2,200) and sometimes imprisoned. "It is like something out of the Cultural Revolution," a Western activist said. "Police put up posters saying it was the duty of all Chinese people to arrest and denounce the refugees."

A report released a week ago by the humanitarian aid organisation Médecins sans Frontières said Beijing launched a new nationwide manhunt in early December. By mid-January it had deported 3,200 North Koreans as part of a "100-day campaign". More than 1,300 are awaiting deportation in detention camps in Tumen and Longjing, both towns in Jilin province.

Once captured, many defectors are released after a few months of beatings and confessions – unless they are Party officials or army officers, in which case they are considered guilty of treason.

The crackdown was still harsher in North Korea, where up to 100,000 Christians are said to be in jail. Terrible stories filter through about the fate of those caught. One report said that in December 2000, a small group of Christians in Chongjin on the north-east coast were discovered at a prayer meeting. The 11 men were beheaded at a public execution and the women and children sent to labour camps.

The situation is so serious that many activists have decided that the only option is to draw international attention to the Christians' plight.

First, a coalition of non-governmental organisations (NGOs) helped a family of refugees seek asylum inside the Beijing offices of the UNHCR, which has stood by helplessly as China refused requests to process the North Koreans as asylum-seekers, saying they were "economic migrants".

Last March, when a group of 25 refugees ran into the Spanish embassy, the campaign gained still more publicity. A spate of similar incidents forced the Chinese to throw a cordon of barbed wire and extra guards around all diplomatic buildings.

China has also been alarmed by suggestions that it should open its doors to a flood of refugees to precipitate North Korea's collapse, the very thing it wishes to prevent.

In the latest effort, NGOs tried to organise the flight of a party of "boat people", but earlier this month the Chinese caught 60 North Koreans and three aid workers as they prepared to leave China on two boats from Yantai in Shandong province. The arrests prompted protests from Seoul and from the United Nations and renewed determination to carry on with the exodus.

"This was only the first step ... You can be sure that we will try another one," said Norbert Vollertsen, a German activist who has been organising the publicity stunts for 18 months. "We are trying to get high-ranking refugees as a next step ... There are more and more high-ranking people in North Korea who want to defect."