Lee Min Bok stared across a narrow inlet at the Korean shoreline, using his compass to gauge the gusting wind's direction. Nodding, the gaunt, soft-spoken missionary then said a prayer with his three assistants and began launching hundreds of helium balloons across the world's most heavily fortified border.

The balloons carried plastic bags containing pamphlets of Bible scripture and pairs of nylon stockings to entice wary North Koreans. Lee's aerial evangelism was part of a broader campaign by Christian groups in East Asia and beyond against North Korean leader Kim Jong Il and his government.

"Christians have become the alpha and omega of the North Korean issue," said Douglas Shin, a California-based Korean American missionary, who was briefly detained by Mongolia in the 1990s for helping North Korean refugees cross the border to Mongolia from China.

"We have picked up this banner to help the North Korean people. Some people don't like using the word crusade, but that's exactly what this is -- a crusade to liberate North Korea."

Hoping to kindle opposition in the isolated communist state, missionaries are smuggling in Bibles, food, clothes, and transistor radios capable of receiving foreign transmissions over the border, mostly via China. The Chinese government does not condone smuggling across its 880-mile border with North Korea, but the size of the frontier makes most activity difficult to monitor.

Ongoing campaigns in South Korea to provide such material is considered seditious by the North, where possessing a Bible is punishable by death or imprisonment. The spread of Bible teachings directly challenges religious teachings in North Korea, where the country's late founder, Kim Il Sung, and his son, Kim Jong Il, are referred to as gods.

"The most dangerous thing for Kim Jong Il is the truth. That's the message I'm sending home," said Lee, 65, a chemist who defected from North Korea in 2000. Lee was detained and questioned for his activities for six hours late last month by South Korean police. But he and his Seoul-based team were back with their balloons on another part of the border three days later.

"We will pave the road to freedom in North Korea with our work," he said.

Missionaries have also become the primary lifeline for people fleeing North Korea.

One woman said she was able to stage a risky operation with the help of missionaries three months ago to get her 20-year-old son out of North Korea, and said she paid $3,000 in bribes to North Korean and Chinese officials.

The woman, Ms. Kim, 50, who asked that her given name be withheld to protect her extended family back home, fled North Korea with her daughter three years ago.

"Sometimes I just have to go over and touch his face -- I can't believe he's here," Kim said as she looked at her son in the office of the Seoul-based Peace Unification Christian Church.

Scant intelligence on North Korea has made it difficult to measure the effect of missionary efforts inside the country, but proselytizing and effecting change through religion is exceedingly difficult, according to analysts who study the region's missionary activities, and to U.S. and South Korean officials. A record 1,890 North Korean refugees settled in South Korea last year, officials said. Refugee groups estimate that 90 percent of the refugees arrive via a network of safe houses along the Chinese border as well as through Mongolia and Southeast Asia. Officials estimate that tens of thousands of refugees are living illegally on the Chinese side of the border with North Korea.

Chinese authorities have arrested 43 South Korean and American missionaries for helping North Koreans since 2001. At least seven are believed to remain in custody, according to a recently released South Korean congressional report.

The Chinese government, which maintains a policy of repatriating North Korean refugees whom they catch crossing the frontier, has cracked down in recent months as more refugees have attempted to cross. A third fewer refugees left North Korea between January and June compared with the same period last year, according to South Korean reports.

Missionaries say they have stepped up efforts over the past four years as North Korea has gradually loosened trade restrictions over its border with China. Several religious organizations have taken advantage by smuggling radios into North Korea. The radios provide a previously unavailable source of information in a society where broadcasts are mostly limited to government-approved propaganda.

Religious groups say they have also boosted the shipment of palm-sized Bibles into North Korea, sending in 10,000 this year in the hopes of nurturing underground churches or underground cells of Christians privately opposed to Kim's rule.

Christian groups, ardent backers of the Bush administration's hard-line policy on North Korea, are trying to heighten outrage about North Korea in the United States by focusing on testimony from defectors about harrowing cases of torture and killings in concentration camps.

The North Korean government denies the existence of the camps. But the State Department's 2005 Country Report on Human Rights Practices reported that an estimated 150,000 to 200,000 people are held in North Korean political detention camps under harsh conditions.

The Midland Ministerial Alliance, an evangelical group in the United States, staged a benefit concert, "Rock the Desert," last weekend in Midland, Tex., President Bush's hometown. The group was seeking to promote awareness of human rights issues through testimony from North Korean defectors, according to Deborah Fikes, the organization's executive director.

Religious groups are working with North Korean opponents on their visits to the United States, including Kang Chol Hwan, a dissident author who met privately with Bush in June. Evangelical lobbying groups such as the Southern Baptist Convention's Ethics and Religious Liberty Commission promoted the passage by Congress of the North Korean Human Rights Act, which was signed into law last fall.

Before the division of the Korean Peninsula in 1945, the northern half of Korea had half the population of the south but almost three times as many Christians. Missionaries liked to refer to Pyongyang, now the capital of North Korea, as "the Jerusalem of the East."

After the 1950-53 Korean War, Christianity became politically linked in South Korea to the anti-communist movement. Unlike other Asian nations, such as Japan, that staunchly resisted waves of Western missionaries, South Korea became one of Asia's largest Christian countries, and now has 12,000 missionaries around the world -- a number second only to the United States.

North Korea contends that it grants religious freedom, and there are three Christian churches in Pyongyang often shown to visiting foreigners. But analysts describe decades of harsh campaigns to eradicate religion in North Korea and replace it with an elaborate political cult that exalts the Kim clan. Kim Jong Il, for instance, is said to have been born on a sacred mountaintop, his birth heralded by lighting bolts and a double rainbow.

Kim Jong Il remains firmly in charge in North Korea, despite reports of severe famines and repression under his rule. But missionaries say the Kim cult helps them in their crusade because it sometimes imitates Christianity. North Korea's Workers' Party, for example, lists 10 "Life Policies" borrowed loosely from the Ten Commandments. And the words to some well-known gospel hymns have been rewritten North Korea to hail the Kims instead.

"We know all the songs; we've sung them for much of our life, but with Kim Il Sung and Kim Jong Il as our lord and son," said Kang Chul Ho, 37, who defected from North Korea in the late 1990s and is now a preacher at the Peace Unification Christian Church. "We're singing a new song now. The idea is that one day many more North Koreans will, too."

Special correspondent Joohee Cho contributed to this report.

Lee Min Bok, 65, a North Korean defector, smuggles Bibles to kindle opposition there. "The most dangerous thing for Kim Jong Il is the truth," Lee said. Lee's Seoul-based team of Christian evangelicals send Bibles to the North two to three times each week. Southern missionaries are also a lifeline for refugees.