Christians in officially-atheist China are braving the wrath of authorities as they put back crosses atop their churches that were knocked down by the police in Zheijang province, home to "China's Jerusalem."

A group of Protestant churches is fighting back as police have knocked down over 450 crosses since 2013, The Christian Monitor reported. Police with large cranes often show up unannounced and remove the crosses on churches ostensibly as part of a new religious structures building code but what many observers regard as the continuing anti-Christian campaign in Asia's biggest country.

The new building policy requires that crosses are removed on top of the churches, reduced in size and placed instead on the side of the edifice in the same colour as the building, making them difficult to see.

In some cases, the elderly members of the 16 churches around the cities of Lishui and Fuyang have replaced the crosses removed from their churches as many as three times in a single day, using raw lumber as replacement crosses.

In one case, police even demolished an entire Christian sanctuary, the $5-million Sanjiang edifice in Wenzhou, just before the completion of its construction, the Christian Monitor report said.

Last month, the Chinese authorities in the province announced that crosses must come off all churches.

That elicited a response from the region's largest evangelical church in the form of a rare open letter, which stated that the policy is "likely to cause chaos ... and religious conflicts."

"The churches are restoring their cross over and over again," said Zan Aizong, a local evangelical and former journalist. "They are being bold and very courageous."

Official "Three-Self" churches — which are legal, registered, and consider themselves loyal to the Chinese state — are often targeted. The leadership of Chongyi Christian church in Hangzhou – one of the largest mega-churches in China with more than 10,000 visitors per week – posted a protest letter on its web site which disappeared after one week.

The letter is described by Teng Biao, a human rights lawyer from Beijing now in residence at Harvard Law School in Cambridge, as "important, since the Three-Self churches tend to be supportive of the government."

The Chongyi Church said the nation is bound to "rules that respect the traditions and customs of all religions" following the Constitution. Efforts to remove a fixture that has been a sign of "faith and love for 2,000 years" atop churches show a lack of respect, the letter said.

The letter argued that building and architectural codes are planned to be suited for specific locations and that an overly extensive ban on all crosses goes beyond the limit of the code.

Knocking down crosses is also tantamount to "excessive interference" by the government and is "likely to cause chaos in execution and religious conflicts," with the new rules for all religious buildings only applicable to Protestants and Catholics, the Church said.

Christian pastors are concerned that the Chinese government is only starting to warm up in preparation for a larger crackdown on China's Christian population.

The anti-Christian campaign now includes infiltration of congregations in Wenzhou to reveal party members and their families who worship.

There are around 50 million to more than a hundred million Protestants and nearly six million Catholics in the country, ruled by the Communist Party which has 70 million members. Of the Christian population, 1.2 million evangelicals are in Wenzhou.