Police arrested the senior pastor of one of the largest unregistered churches in Beijing on Saturday and have put many congregants under house arrest for trying to hold Sunday service outdoors, said a rights group focused on religious freedom in China.

Senior Pastor Jin Tianming, who founded the 1,000-member Shouwang Church in the 1990s, was detained yesterday after his church intended again to attempt to hold worship service outdoors, according to Texas-based China Aid Association.

Last week, hundreds of church members were arrested and then released when they tried to hold service at an open-air venue.

Leaders of Shouwang Church have repeatedly asserted that the outdoor gathering is not politically motivated. They claim that their members are forced to worship outdoor because the Chinese government has prevented them from securing a permanent space for service.

The church was evicted from the restaurant it was previously meeting at and officials reportedly pressured a landlord from turning over the keys to a building Shouwang Church had purchased for more than $4 million.

“We urge the Chinese government to exercise restraint and refrain from using violence that would further escalate the conflict with peaceful Shouwang worshippers who ask for nothing more than simply to exercise their right to religious freedom,” said China Aid founder and president Bob Fu.

The Chinese government, as of late, has increased its crackdown on dissidents and protesters, according to the U.S. State Department’s report on human rights released this week.

"In China, we’ve seen negative trends that are appearing to worsen in the first part of 2011," said Secretary of State Hillary Clinton.

Clinton highlighted that dozens of lawyers, activists, bloggers and others who challenged the Chinese government’s authority have been arrested for exercising their “internationally recognized right to free expression.”

Many believe that China’s crackdown comes out of its fear of possible revolts as some citizens, inspired by the uprising in the Arab world, call for “Jasmine” protests.

Given the government’s current sensitivity towards dissent, a gathering of hundreds of non-registered Christians in plain public view would be a threat.

In China, it is illegal to take part in religious organizations outside of the state-sanctioned faith bodies. For Protestant churches, this means they must register with the Three-Self Patriotic Movement and China Christian Council (TSPM/CCC) in order to operate legally.

But many churches choose not to register with the TSPM/CCC based on the principle that Jesus is the head of the church and not the government. Unregistered churches in China are often called “house” or “underground” churches.

Shouwang, one of the largest house churches in Beijing, is likely facing especially harsh pressure from the Chinese government because the incident has received much international media attention and authorities are portrayed in a negative light.

Besides detaining Senior Pastor Jin Tianming, authorities are also said to have pressured landlords to evict church members from their homes, and to have detained another Shouwang pastor, Li Xiaobai, and his wife.

At the moment, the whereabouts of Pastor Jin Tianming is unknown.

According to CAA, more than a dozen house churches in Beijing have joined to issue a statement in support of Shouwang Church and in calling for a weekly prayer vigil for the congregation and its leaders.