JEJU, South Korea—One Sunday afternoon in the fall of 2019, a congregation of Christians in China’s southern city of Shenzhen crammed into a rented office space to debate one of the biggest decisions of their lives: whether they should stay in China or seek exile in South Korea.

Chinese authorities regard the Shenzhen Holy Reformed Church, an unregistered “family church” founded in 2012, as illegal. Its members say they have faced government harassment for years. Some members felt the pressure had grown too much to bear.

Over three hours, more than 50 debated the proposal. Some wanted to leave to ensure their children could continue their religious schooling. Some worried about finding jobs, or being forced back to China. Emotions ran high and tears were shed, participants recalled.

When the church reconvened for a vote the following Sunday, the result was decisive: 56 members in favor of relocating versus 17 against.

Children make up about half the group, all of whom have had their asylum applications rejected at least once.

Children make up about half the group, all of whom have had their asylum applications rejected at least once.

Photo: Jun Michael Park for The Wall Street Journal

Under China’s leader, Xi Jinping, the Communist Party has tightened control over all aspects of society, from business to religion, and suppressed dissent with growing vigor. That has pushed more ordinary Chinese to try to leave.

Millions of refugees fled China throughout the 20th century amid civil wars, invasion, and Mao Zedong’s tumultuous rule. Outflows shrank after economic overhauls lifted living standards but have grown again in recent years. The United Nations refugee agency counted more than 105,000 asylum seekers from China as of mid-2020, up from 15,362 at the end of 2012, the year Mr. Xi took power.

Human-rights experts say they hadn’t encountered cases involving congregations seeking asylum en masse, however. Many Chinese Christians say religious freedoms have narrowed since 2018, when new regulations imposed greater curbs on religious activities.

Having moved to Jeju, a Hawaii-like resort island off the southern tip of South Korea that has Christian churches, the congregation now faces new challenges, with many members eking out meager livelihoods while navigating a slow asylum process.

“ ‘There’s no way back for us.’ ”

— Pan Yongguang, church pastor

More than 60 church members filed for asylum and all have had their applications rejected at least once. They are allowed to stay in Jeju while pursuing legal challenges, a process that can last several years. Of the nearly 12,000 refugee applications South Korea reviewed in 2020, it accepted just 0.4%, according to Nancen, a refugee-rights center in Seoul.

The church’s pastor, a 43-year-old former doctor named Pan Yongguang, said he recently told an American diplomat who visited the congregation in late May that the church hopes to be resettled in the U.S., though it isn’t clear whether Washington will support that.

Many church members, unable to speak Korean and with uncertain legal status, have taken menial farm jobs.

Many church members, unable to speak Korean and with uncertain legal status, have taken menial farm jobs.

Photo: Jun Michael Park for The Wall Street Journal

In response to queries, the State Department said its officials regularly meet with religious groups to promote religious freedom. The U.S. Embassy in Seoul separately said it has discussed the church’s situation with South Korean officials. South Korea’s Foreign Ministry declined to comment.

China’s Foreign Ministry said it wasn’t aware of the church’s circumstances. While the government guarantees religious freedom, “no one should make use of religion to carry out illegal activities,” it said.

In 2001, Mr. Pan quit his job as a doctor and moved from his native city of Yunfu to Shenzhen, where he found an administrative role in a local company. After completing theological training under pastors from a U.S.-based Reformed Presbyterian church, he started his own Presbyterian church in 2012.

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His flock grew to more than 120 people. Mr. Pan rented office space for weekly services and church-school classes.

While local authorities occasionally detained and questioned Mr. Pan over his church activities, officials were generally cordial, he said. Such geniality disappeared after the new religious regulations implemented in 2018 tightened oversight on religious activities and funding.

While China’s constitution grants people religious freedom, the officially atheist Communist Party is wary of institutions that it sees as potential threats to its rule and tightly regulates faith groups and activities.

Officials said the regulations were meant to prevent extremism and protect religious harmony. Mr. Pan joined more than 450 other Chinese church leaders in signing a petition against the rules.

Shenzhen officials grew increasingly insistent on shutting down the church and its religious education program, Mr. Pan said. “They said, ‘You should inculcate our beliefs, teach the children to listen to the party and follow the party,’” he recalled.

Top: Pan Yongguang, the church’s pastor, says the attitude of local Chinese authorities to the church hardened in 2018 when new regulations tightened oversight. Bottom: The pastor’s bookshelf is full of theology books.

Top: Pan Yongguang, the church’s pastor, says the attitude of local Chinese authorities to the church hardened in 2018 when new regulations tightened oversight. Bottom: The pastor’s bookshelf is full of theology books.

Photo: Jun Michael Park for The Wall Street Journal

Authorities detained a friend of Mr. Pan’s who organized the petition—later sentencing him to nine years in jail for inciting subversion. In 2019, officials pressured Mr. Pan’s landlord into evicting him and his family, and stopped him from traveling to Thailand for theology classes, he said.

Church leaders started planning to leave. Many members who were willing to leave were migrant workers who had children attending the church school and saw their lives as inseparable from the church. Some younger and single church members with office jobs were reluctant to give up relatively comfortable lives in Shenzhen.

Chen Jingjing, a 30-year-old former factory worker, said she didn’t want to go but ultimately agreed so that her two sons, who will turn 3 and 6 this year, wouldn’t be exposed to China’s state schooling system.

“All day, from morning to night, it’s all Xi Jinping—more and more, it stands in opposition to faith,” she said.

Wen Wensheng, a church elder, left with his pregnant wife and two children just hours after the vote. To pass off as tourists, his family brought only bare essentials, stuffing clothes, Bibles and snacks into two 20-inch suitcases and two small backpacks. They had sold or given away most of their other belongings.

Chen Jingjing was reluctant to go to South Korea but decided to do it for her two young sons.

Chen Jingjing was reluctant to go to South Korea but decided to do it for her two young sons.

Photo: Jun Michael Park for The Wall Street Journal

“Am I really committing treason?” Mr. Wen recalled thinking. “But I looked at my children and their future, and I told myself, stay firm and be a bit braver.”

While Mr. Wen and his family were allowed into Jeju, several church members were turned back by immigration officials who suspected they were coming to work illegally.

“ ‘Am I really committing treason?’ ”

— Wen Wensheng, church elder

One faced retribution when she returned home, said Mr. Pan, who kept up with members through China’s WeChat messaging app. State-security officials raided the woman’s home and confiscated electronic devices and religious books, he said. Then they asked her to sign papers renouncing her Christian beliefs and ties with Mr. Pan’s church. She refused and authorities have restricted her movements, Mr. Pan said.

More recently, authorities raided the home of another church member who didn’t leave China and questioned him over his religious activities, Mr. Pan said. The Wall Street Journal wasn’t able to reach these two church members or independently verify their accounts.

In all, about 60 church members, including nearly 30 children, settled in Jeju by early 2020. A local church lent them space for Mr. Pan’s sermons.

Top: Wen Wensheng and Luo Guangying with their three children, March 7; they brought only bare essentials when they left China. Bottom: Ms. Luo hanging laundry with the help of her son, March 8. She was pregnant with their youngest child when the family fled.

Top: Wen Wensheng and Luo Guangying with their three children, March 7; they brought only bare essentials when they left China. Bottom: Ms. Luo hanging laundry with the help of her son, March 8. She was pregnant with their youngest child when the family fled.

Photo: Jun Michael Park for The Wall Street Journal

Unable to speak Korean and with uncertain legal status, many took menial jobs on farms, picking tangerines or other crops. Mr. Wen found work harvesting kohlrabi, a type of cabbage. He said he can’t clench his fist on some nights because of the pain in his hand from harvesting using scissors.

As winter set in, doubts deepened. Several families wanted to return to China, even if it meant punishment. But by then, China had virtually closed its borders due to Covid-19.

One church elder—You Guangbo, a father of two—said he gave up his position as a project manager at a Shenzhen factory and wound up with a lower-level job making agricultural tents, and lost close to 20 pounds.

“This isn’t the road I wanted to travel,” said his wife, Dan Xiaoli, bursting into tears as she described working in Jeju fields in rain and snow. “Sometimes I think, ‘How great was my life in China? My husband could support us, I could lie around doing nothing if I wanted. Why do I have to suffer like this?’ But then I think, ‘This is temporary.’”

In March, members started receiving phone calls they interpreted as warnings to return home. South Korea’s consulate in Guangzhou called a church member and asked if he had overstayed his tourist visa in Jeju, Mr. Pan said. The consulate said it routinely makes such calls to check on suspected overstayers.

“ ‘This isn’t the road I wanted to travel.’ ”

— Dan Xiaoli, church member

Three church members in Jeju, meanwhile, received calls from someone claiming to be from the local Chinese consulate. The caller said a package had arrived for them, though the number didn’t match the consulate’s publicly listed landline, Mr. Pan said. The members didn’t go.

Mr. Pan said the church voiced concerns over these calls to the U.S. diplomat who visited in May, and gave him a Chinese edition of William Bradford’s “Of Plymouth Plantation,” a journal that documented the story of the Pilgrims who arrived in America on the Mayflower in 1620.

Wang Fang, Mr. Pan’s wife, taking a break in a garlic field in Jeju’s Hangyeong township, March 8.

Wang Fang, Mr. Pan’s wife, taking a break in a garlic field in Jeju’s Hangyeong township, March 8.

Photo: Jun Michael Park for The Wall Street Journal

During one recent Sunday sermon, Mr. Pan read a passage about Noah, Abraham and other figures who followed their faith into the unknown.

Mr. Pan said he tells members that any suffering they face is part of God’s plan. One family of five withdrew from the church last month, citing concerns over Chinese government pressure, while staying in Jeju to continue their asylum bids. Other members said they were slowly adjusting—and were hoping they made the right decision for their children.

“There’s no way back for us,” Mr. Pan said.

—Andrew Jeong in Seoul contributed to this article.

Write to Chun Han Wong at chunhan.wong@wsj.com and Josh Chin at Josh.Chin@wsj.com