CHENGDU, China — For months, Gu Baoluo had been looking forward to a boisterous Christmas celebration at one of China’s best-known Protestant churches. He loved decorating trees, singing songs like “Silent Night” and watching the annual Christmas pageant recounting the birth of Jesus.
But in early December, the police shut down Mr. Gu’s usual place of worship, the Early Rain Covenant Church in the southwest city of Chengdu, as part of what activists say is the most severe crackdown on Christianity in more than a decade. The police confiscated Bibles, shuttered a school and seminary run by the well-known church and detained Early Rain’s outspoken pastor on charges of “inciting subversion,” punishable in serious cases by at least five years in prison.
On Christmas Eve, Mr. Gu, 31, a rice seller, went to the only safe place to worship that he knew: a friend’s home, where he recited hymns and prayed for the two dozen Early Rain members that are in detention. Fearing that he and his friends might be arrested, Mr. Gu used encrypted chat apps to share information about surveillance and harassment by the police.
“We will not forfeit our faith because of suppression by the authorities,” Mr. Gu said.
As millions around the world gather to celebrate Christmas, China is capping a year in which the government of President Xi Jinping has led an unrelenting campaign against unofficial churches in China, which by some estimates serve as many as 30 million people.
Mr. Xi, apparently concerned that independent worship might pose a threat to the ruling Communist Party’s dominance over daily life in China, has sought to bring Christianity more firmly under the party’s control. The government this year banned online sales of the Bible, burned crosses, demolished churches and forced at least a half-dozen places of worship to close.
The campaign comes as Mr. Xi, the most powerful Chinese leader since Mao Zedong, has worked to more aggressively control religion across China, including the detention of thousands of Muslims in the western region of Xinjiang.
Renee Xia, international director for China Human Rights Defenders, an advocacy group, described the effort as targeting the “heart of the underground Christian resistance.” The government has focused its campaign on unofficial Christian churches that promote ideas like social justice or have been critical of the party’s grip on society.
“The message,” Ms. Xia said, “is that Xi can’t be messed with.”
The crackdown has escalated in the weeks leading up to Christmas. The police this month shut down the 40-year-old Rongguili Church in the southern Chinese city of Guangzhou, which attracted thousands of worshipers. And in September, the authorities in Beijing ordered the closure of the 1,500-member Zion Church, one of the largest unofficial churches in the capital.
The government requires religious groups to register, though many still worship in unofficial churches, sometimes called underground or house churches.
Many in the party believe Christianity, which by some estimates is China’s fastest-growing religion, promotes Western values and ideals like human rights that conflict with the aims of China’s authoritarian government and Mr. Xi’s embrace of traditional Chinese culture and Confucian teachings that emphasize obedience and order.
But the government’s heavy-handed efforts to obliterate several high-profile churches have been met with resistance among Christians.
On Christmas Eve, the authorities posted a sign at Early Rain’s former headquarters saying its 23rd-floor sanctuary had been converted into office space for the local government.
Li Shuangde, a teacher in Chengdu who has been part of Early Rain since 2011, said that church members had been asked by the authorities to sign letters stating that they no longer believe in Christianity. He said Early Rain had no choice but continue to exist in secret. “We have moved underground,” he said.
Members have continued to hold Sunday services, sometimes on the banks of a river near the church’s former headquarters in a downtown high-rise. They have called for the release of detained leaders, including Wang Yi, the pastor of Early Rain, and his wife, Jiang Rong.
Mr. Wang, in a prewritten message released after his detention, spoke about the importance of disobedience.
“The Communist regime’s persecution of the church is an extremely vicious crime,” he wrote. “As a pastor of the Christian church, I must strictly and publicly condemn such crimes.”
Mr. Wang had been scheduled to deliver a Christmas Eve sermon at Early Rain titled “The God Who Bestows Peace.” Instead, hundreds of Early Rain members on Monday scattered across Chengdu for services inside the homes of friends and relatives or at welcoming churches.
At Chengdu Xishuipang Reformed Church, a Protestant church with close ties to Early Rain, more than 100 people gathered inside a worship hall on the 16th floor of an apartment building.
A children’s choir sang “Silent Night,” and a small Christmas tree, decorated with snowflakes, was on display near the lectern.
The anxieties brought on by the recent arrests hung over the ceremony.
“If you see the police, national security or community workers greet them with gentleness,” Wen Hongbin, an elder at Xishuipang, told the congregation. “If they try to grab the microphone, I ask the brothers sitting in the front row to please stop them.”
While he did not explicitly mention Early Rain, Mr. Wen asked those in attendance to remember “those who are criminally detained.” Then he began a sermon about the meaning of Christmas and the sacrifice made by Jesus.
Since Mr. Xi rose to power in 2012, the authorities have led a sustained campaign against unregistered churches. In one province, more than 1,500 crosses were removed from churches from 2014 to 2016, according to advocacy groups.
This year, some Chinese cities have banned Christmas displays. But the government also allows some degree of celebration, in part to stimulate the economy. Here in Chengdu, the capital of Sichuan Province, Christmas trees stand side by side on city streets with propaganda posters, and music from “The Nutcracker” plays in the background at malls.
Officials in the United States have denounced the Chinese government’s efforts to limit the spread of Christianity.
“China’s Christians and other faith communities are under siege and treated as enemies of the state for daring to worship and peacefully live out their faith,” Senator Marco Rubio of Florida and Representative Chris Smith of New Jersey said in a joint statement condemning the recent detentions.
But China’s growing influence in world affairs has shielded it from some criticism.
One notably silent voice: the Vatican, which in September reached a provisional deal with the Chinese government to end a decades-old power struggle over the right to appoint bishops in China. The Vatican said it sent a delegation of leaders to China this month to work out details of the agreement, but declined to comment on the crackdown on Christian churches.
Despite Mr. Xi’s efforts to expand the officially atheist party’s control of worship, religious life in China is flourishing.
While official figures are imprecise, experts believe there are about 60 million Christians in China, with roughly half worshiping at state-sanctioned churches and half at unofficial churches.
Independent churches like Early Rain, with more than 500 members, have attracted large followings in recent years, especially among white-collar workers seeking an escape from rampant materialism at the center of modern Chinese life.
While sermons at state-sanctioned churches are often tightly scripted, independent churches boom with searing indictments of corrupt officials and rousing calls to protect the rights of the poor.
Early Rain, which Mr. Wang founded in 2008, was among the most daring. Mr. Wang called Mr. Xi a sinner, held prayer sessions each year to mark the brutal crackdown on pro-democracy demonstrations around Tiananmen Square in Beijing in 1989, and organized a fund to support relatives of political prisoners in China.
Mr. Gu, the rice seller, began attending services two years ago after finding videos of Mr. Wang’s fiery sermons online. He felt Mr. Wang’s concern for the poor was in line with his own view that the government was abusing workers and violating human rights by destroying their homes to make way for expensive developments. Mr. Gu was baptized last year.
“I saw injustices in society,” Mr. Gu said. “I saw that the government’s promotion of China as a just country that enforces laws in a civilized manner was all a lie.”
Worried for his own safety, Mr. Gu recently closed his business, hoping to avoid government scrutiny. He said he has grown fearful as he has watched the police arrest his friends.
Mr. Gu has turned to the Bible in recent days for support. Sometimes, he recites a verse from the Book of Proverbs: “The path of the righteous is like the morning sun, shining ever brighter till the full light of day.”