China has intensified its crackdown on religion, with images emerging of crosses being burned and destroyed at Christian churches.

Key points: Church officials say authorities are ordering the removal of signs of faith

Church officials say authorities are ordering the removal of signs of faith Churches beginning to look more like "culture clubs"

Churches beginning to look more like "culture clubs" Vatican and China reach deal on appointment of bishops

The crosses are said to often be replaced with objects such as the Chinese flag and photos of Chinese President Xi Jinping and former Communist Party leader Mao Zedong.

In one video posted on Twitter earlier this month, fire is seen engulfing the cross at the Chinese Christian Church in Xinxiang city, in the country's central Henan province.

Liang Zhang, 48, the pastor of a house church in Henan's Shangqiu city, said the state had been tightening its control over church operations.

"In the beginning, they said that children would not be allowed to enter, and signs on the outside should be removed, including the cross and other signs of faith," Mr Zhang told the ABC.

"And then they came into the church saying that things inside should be removed.

"For example, the banner saying: 'For God, so love the world' and the scriptures were torn down, and all things related to the Bible and faith had to be cleared out."

Photos of Chinese President Xi Jinping and former Communist Party chairman Mao Zedong flank a cross inside a church. ( Supplied: Liang Zhang )

China's campaign to 'Sinicise' religion

Several videos sent by Mr Zhang to the ABC, and others circulating on social media, appear to show the forced destruction of crosses and changes to churches' appearances.

Authorities make changes to the exterior of a church in Zhengzhou city, Henan province. ( Supplied: Liang Zhang )

In some videos, which Mr Zhang said were filmed recently in Henan, authorities use cranes to take down crosses, while others show officials forcing their way into underground churches.

The campaign corresponds with the Government drive to "Sinicise" religion by demanding loyalty to the officially atheist Communist Party and eliminating any challenge to its power over people's lives.

Mr Zhang said the clampdown had become more dramatic in recent months, with even state-sanctioned churches targeted.

"Since June, they started to ask us to tear down things about Sunday School for kids," Mr Zhang said.

"[Many] of the big official TSPM churches and the family churches were closed down," he added, referring to the Three-Self Patriotic Movement, a state-sanctioned church.

Mr Zhang said the Government was installing "information officers", who report behaviour that is anti-government or seen as a threat to social stability, in churches.

He said the only places where the Bible could be discussed freely were small church setups in houses, where 20-30 people could gather.

Million of Chinese attend underground churches like this Protestant one in Beijing. ( Supplied: Wayne Mcallister )

Under Chinese law, religious followers are only allowed to worship in congregations registered with authorities, but many millions belong to so-called underground or house churches that defy government restrictions.

Mr Zhang said dozens of churches had been shut down in his county and those remaining were beginning to "look like culture clubs" rather than religious buildings.

"All of the … religious facilities inside the church have been removed [and] the national flag will have to be hung at the gate before October 1st," he said.

"We now have our cross in the middle of our presidents' portraits, which are President Xi and Chairman Mao's portraits."

The latest tightening of control follows moves earlier this year to pull bibles from sale through online bookstores across China, sparking outrage from Chinese Christians.

Sorry, this video has expired There was no official statement on why the Bible was removed from online bookshops (Photo: Supplied/Wayne Mcallister)

Crackdown comes as Vatican reaches deal with China

The crackdown on religion was continuing even as Beijing was negotiating a landmark deal with the Vatican over the appointment of bishops.

On Saturday, the Vatican signed an agreement giving it a long-desired and decisive say in the appointment of bishops in China, though critics labelled it a sell-out to the Chinese Government.

China has been appointing bishops without the Pope's consent. ( AP: Alessandra Tarantino )

The deal resolved one of the major sticking points between China and the Vatican in recent years, with the Vatican agreeing to accept seven bishops who were previously named by Beijing without the Pope's consent.

The Vatican has said the accord, a breakthrough after years of negotiations, was "not political but pastoral", and hoped it would lead to "the full communion of all Chinese Catholics".

Bob Fu, the founder of Christian human rights organisation ChinaAid, was among those to hit out at the agreement.

"While we understand the eagerness of Vatican for seeking more legitimacy in the eye of the Chinese Communist Party, this reported deal is nothing but a betrayal of both the millions of suffering persecuted Christians in China and the global Catholic Church," he said.

Joseph Zen, a Chinese cardinal of the Catholic Church in Hong Kong, said the deal lacked detail and helped empower the Government.

"With the agreement the [Chinese] Government can tell the Catholics: 'Obey to us! We are in agreement with your Pope!'"

Authorities remove a cross topping Ao Huan Christian Church. ( Supplied: Wayne Mcallister, file )

With wires