BEIJING — It has all the trappings one would expect from the capital’s most well-heeled and prestigious Christian congregation: a Sunday school for children, nature hikes for singles and clothing drives for the needy. Last year, the church, called Shouwang, or Lighthouse, collected $4 million from its 1,000 members to buy its own house of worship.

But Shouwang, according to China’s officially atheist Communist Party leadership, is technically illegal, a so-called house church that in recent years had come to symbolize the government’s wary tolerance for big-city congregations outside the constellation of state-controlled churches, a release valve for an educated elite seeking a nonpolitical refuge for its faith. That is, until now.

Evicted yet again from its meeting place by the authorities, Shouwang announced this month that its congregants would worship outside rather than disband or go back underground. Its demands were straightforward but bold: Allow the church to take possession of the space it had legally purchased. The government responded with a clenched fist.

On Sunday, for the second week in a row, the police rounded up scores of parishioners who tried to pray outdoors at a public plaza. Most of the church’s leadership is now in police custody or under house arrest. Its website has been blocked.

"We are not antigovernment, but we cannot give up our church family and our faith," Wei Na, 30, the church choir director, said last week just before more than 160 congregants were corralled onto buses and detained. "Satan is using the government to destroy us, and we can’t let that happen."

The move against Shouwang, as well as other house churches, coincides with the most expansive assault on dissent in China in years, one that has led to the arrests of high-profile critics like the artist Ai Weiwei, but also legions of little-known bloggers, rights lawyers and democracy advocates who have disappeared into the country’s opaque legal system. The crackdown, now in its second month, was prompted by government fears that the Arab revolts against autocracy could spread to China and undermine the Communist Party’s six-decade hold on power.

Although many congregations continue to hold services unhindered, in recent weeks the pastors of two large unofficial churches in the southern city of Guangzhou have been detained and their congregations rendered homeless. House church leaders in other places, including Xinjiang in the far west and Inner Mongolia in the north, have reported increased harassment, according to China Aid, a Texas-based Christian advocacy group that tracks cases of persecution.

Last year, the organization reported 3,343 instances in which house church members or leaders were detained or beaten, a 15 percent increase over 2009. Bob Fu, the group’s president, said such incidents were part of the latest government campaign to try to force house church members into state-run congregations.

"I’m not optimistic a peaceful solution will be found to this crisis," he said. "The government’s moves are forcing nonpolitical churches to commit acts of civil disobedience, which the government is not likely to tolerate."

Global Times, a state-owned newspaper that broke new ground last year by writing positively about house churches, gave voice to the most recent shift in official attitude with an editorial last week that condemned Shouwang as trying to "twist Chinese society by politicizing religion" and suggested that overseas Christian groups were using the church to subvert the government.

"All Christians, as well as those of other faiths, are Chinese citizens first and foremost. It is their obligation to observe discipline and abide by the law," the newspaper wrote.

Although house church leaders are careful to say that they have no interest in politics, their insistence on independence from state supervision and their real or imagined associations with foreign churches have stoked deep-seated fears among China’s authoritarian leaders, who have been suspicious of Christianity since 1949, when the Communists took power, branded all missionaries as agents of imperialism and threw them out of the country.

"The bottom line is that house church members believe in Jesus, not the party’s version of Jesus," said Zhang Minxuan, a pastor and president of the Chinese House Church Alliance, who says he has been detained 41 times over the years.

Some experts suggest that two-thirds of China’s estimated 60 million Protestants worship at unregistered churches. Just as noteworthy, at least from the government’s viewpoint, is that a growing number are young, educated urbanites — a demographic traditionally at the forefront of political change in China. (Many house church leaders are veterans of the 1989 pro-democracy protests who turned to Christianity in the bleak years of government repression that followed.)

Beyond the appeal of spirituality and the promise of redemption, many converts say they are drawn by the sense of community and intimacy that flourishes at unofficial churches. Huang Yikun, a 32-year-old magazine editor and Shouwang member, said the congregation provided a tonic against the ills of Chinese society: rampant corruption, media censorship and a society he described as fixated on money and power. "There is something so cold and empty about life outside the church," said Huang, an intense, bookish man who converted three years ago.

Once an idealist who thought he could change China through journalism, Huang grew depressed by the lack of political reform that he had hoped would accompany the 2008 Beijing Olympics. Becoming Christian, he said, removed such expectations because he now believes political change is beyond the power of mortals. "If I didn’t believe in Jesus Christ, I’d probably be more of a rebel," said Huang, who devotes his energies to Bible study and proselytizing among friends and acquaintances, a cornerstone of many unofficial Protestant congregations in China.

Like many underground churches, Shouwang started out small, with 10 people in an apartment that the Rev. Jin Tianming rented near Qinghua University. It was 1993, and to avoid detection by the police, meetings were clandestine. When an apartment became too crowded, the congregation would split and spread to other apartments, a process that was repeated numerous times, especially after police raids.

As strictures eased during the last decade, Jin brought his congregation out of the shadows, renting space in an office building near Beijing’s university district. That same year, in 2006, lawyers in the congregation helped the church apply for legal recognition with the State Administration for Religious Affairs.

With Shouwang’s doors wide open, new parishioners poured in, forcing the church to operate three consecutive Sunday services. The number of paid staff grew to 10 and the congregation started a social welfare program, delivering food to the poor and financial aid to victims of the 2008 earthquake in Sichuan Province.

Shouwang’s latest troubles began again three years ago, shortly after its application for official recognition was denied. Officers from the Beijing Public Security Bureau burst into Sunday services, pronounced the gathering illegal and wrote down the personal details of everyone in the room, one by one. In the days that followed, calls were made to congregants’ employers and, in the case of young people, their college administrators. Many congregants say they were threatened with dismissal from jobs or school if they did not switch to an official church. Some left, but Shouwang’s ranks continued to grow.

In November 2009, after months of pressure from the government, the landlord declined to renew the church’s lease. Congregants met at a park the following Sunday, enduring an unseasonably early snowstorm and drawing foreign media attention. After one more outdoor service, the government offered to find the church a new space. With President Obama set to arrive in China for his first state visit here, church leaders say, Chinese leaders were eager to avoid diplomatic distractions.

But if the government had reached an accommodation, it was only temporary. Church leaders say relations soured last October after 200 Chinese house church members — many of them from Shouwang — tried to join an international congress of evangelical Christians in South Africa. Furious that the group sought to represent China, and indirectly undermine the state-run churches, the authorities stopped all but two at the airport.

Not long afterward, the government injected itself into a real estate transaction between the owner of an office building and the congregation. Although the money to buy space had been delivered and the paperwork signed, the owner refused to hand over the keys. The congregation, in turn, will not accept its money back.

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Even as Shouwang faced its most serious existential challenge last week, Jin was defiant, saying the congregation would continue to gather in public until the government allowed it to occupy its new space.

"I urge the government to come up with a peaceful and responsible solution," said Jin, who was speaking from his apartment, its doorway blocked by the police. "I am fully prepared to go to jail for my church. I belong to the Lord, and if this is what God intended, so be it."