Christian ministers reportedly received strict warnings from Communist party representatives to keep a low profile during celebrations for the National Day of the People's Republic of China on Friday.

According to Zhang Wei (name changed for security reasons), a local contact of the Christian anti-persecution charity Open Doors, some pastors were warned to "behave", "be quiet" and "be invisible in the public domain". If the churches did not 'behave,' their church meetings would run the risk of being stopped.

There were also reports of authorities making regular calls to house church pastors to reiterate their 'boundaries'.

"National Day is an opportunity for China show to the world its great power, and how it is advancing," says Zhang Wei.

"If any undesirable events such as protests, or any anything critical of the State, happen during this period, the government will lose face.

"As the government considers Christianity as western in origin, they see it as a threat of foreign infiltration. Therefore, the authorities warn the churches to minimize its activities."

Pastors who are suspected of conducting church activities other than low-profile regular Sunday services are forced to have "tea meetings" with the officials.

"For ordinary believers, the consequences may be just warnings or registration of their ID," says Zhang Wei. "For leaders and pastors, they would be interrogated for hours, detained overnight and be fined. There can be more severe consequences faced if the churches resist the authorities and cause disturbance."

The current clampdown comes as existing pressure on Christians is steadily tightening: officially-sanctioned churches are being instructed to display the Chinese flag along with the cross and integrate their teachings with "Chinese Socialist principles". There are reports of mass church closures and hundreds of crosses broken down from church buildings with little to no warning.

According to Julia Bicknell of World Watch Monitor, which analyses religious persecution trends, the party is trying to shape Chinese Christianity rather than suppress it: "There are now more Christians in China than members of the Communist Party. Unlike the Uyghurs, they can't detain all Christians. However, they are trying to adapt Christianity to their political mindset and beliefs."

Dr David Landrum, Director of Advocacy at Open Doors UK, said: "By applying the already familiar tools of intimidation, Chinese authorities are trying to make the Christians invisible. Despite their best efforts, the church is not going away anytime soon."