One of the most prominent Protestant figures in China, the Rev. Gu Yuese, has been detained, along with his wife, and held incommunicado as part of what Chinese evangelical leaders say is a broad official crackdown in China on what is described as harmful “foreign influences."

On Friday, state religious authorities in the city of Hangzhou confirmed that Rev. Gu was undergoing a criminal investigation.

Two other prominent Chinese Protestant leaders strongly decried the move by authorities, including Chen Yilu, head of the Nanjing Union Theological Seminary, the official academy in China for pastoral training among Protestants.

“What kind of church system does our Chinese church have?” Mr. Chen asked on social media, criticizing state tampering with the governance of the local church.

Gu, also known as Joseph Gu, is both head of China’s largest Protestant evangelical congregation, the Chongyi church in Hangzhou, China’s first megachurch -- and he sits on China's national Standing Committee for religious authority.

Gu for years had a reputation as a friendly and often conciliatory face for the Protestant church in China. He received foreign delegations and was a reassuring voice for religious freedom in a country ruled by a Communist party. Franklin Graham, son of the prominent American pastor Rev. Billy Graham, preached at his Chongyi church, which numbers some 10,000 adherents.

But moves to discipline Mr. Gu began to take shape, according to members of his church, after he publicly opposed a new law last spring to tear down church crosses in Zhejiang Province on China’s eastern coast. An estimated 1,800 crosses have been forcibly removed in Zhejiang, whose city Wenzhou is often called “China’s Jerusalem” for its large evangelical population.

As Christianity, especially evangelicalism, has grown swiftly in China, it has caused consternation among state authorities as sanctioning a soft but powerful form of authority and loyalty outside the party. By some estimates there are as many or more Christians in China today as there are Communist party members, who number some 83 million.

The cross removal campaign in Zhejiang was widely seen there as a put down and curbing of Christian enthusiasm and identity. Yet the campaign transgressed an invisible line among believers as it took aim mainly at official Protestant churches, sanctioned by the state, rather than at the proliferation of unofficial “home churches” where worship is freer from state oversight. Members of the official Protestant church generally see themselves as more patriotic and rule-abiding.

Last week Gu was removed as chief pastor at Chongyi church by a state-run religious body in Hangzhou, causing shock among the Christian community there and more largely in China.

In a communication to his congregation at the time, Gu warned that further actions may be taken, but that he and his wife, also a pastor at the church, would stay. “Dear family members,” he wrote, “There is a rare freezing cold coming soon to Hangzhou city. Please take care and be sure to rely on Grace … Chongyi Church is also facing an unprecedented situation.”

Chongyi is considered the largest official Protestant church in China, and its preaching and ambiance have been compared to American megachurches like pastor Rick Warren's Saddleback church in Lake Forest, Calif., where Gu has visited.

Taken to 'black jail'

Bob Fu, director of ChinaAid in Texas that provides legal aid to Christians in China, confirmed that Gu was arrested under Article 73 of China’s criminal code and taken away to a “black jail” to await final charges. The process, whose official term is "residential surveillance in a designated location," is the same used to hold some 230 human rights lawyers that were suddenly rounded up in China last July as part of a concerted crackdown on civil society space in the People's Republic.

Mr. Fu thinks it likely that Gu’s attempt to cross authorities and stay at his Chongyi church likely triggered his detention, which is the first step towards his formal arrest.

“This is really quite an escalation,” says Fu. “It sends a signal to silence any potential future dissenting voices from within the church. It tells everyone to shut up.”

The leader of the Protestant church in Hunan Province, Rev. Chen Zhi, on Tuesday posted a comment on the Chinese Internet forum Weibo that Gu was relieved of his church post due to his public opposition to the province-wide policy of cross removals, seen as provocative among believers.

Rev. Chen also denounced the “traitors of faith like Judas” in Gu’s local Hangzhou community that voted him out of his job.

Carsten Vala, an authority on Christianity in China at Loyola University Maryland, says the action against Gu appears to show that political or civil space in China outside the party is shrinking.

“What is most worrying is that the crackdown on lawyers and civil society activists is now even reaching into the circles of officially registered religious and social organizations,” Mr. Vala says. “Not just unregistered groups.

After all, Pastor Gu is a leader of the official churches of the Chinese Communist Party-backed Three Self Patriotic Movement association.”