The Chinese government's crackdown on churches is showing no sign of slowing down, as at least four Christians were severely injured during a clash with officials yesterday morning.

At 3am local time on 21 July, International Christian Concern (ICC) reports that 400 police officers attempted to remove a cross from the roof of Sjuitou Salvation Church in Wenzhou, Zhejiang province, about 500 kilometres south of Shanghai.

Members of the church have been guarding the building for the past month following several threats of demolition from government authorities. Pastor Zhan Yingsheng last week resigned from his position and said he will now dedicate his life to fasting, praying and preparing to be martyred for his faith.

In a letter written on July 17, Pastor Zhan shares his concern at the government's increased persecution of Christians, and insists he is not "making a show or trying to get some publicity" but "as a Christian facing unrighteousness, my conscience urges me to do my duty. I wish to better understand the meaning of 'Christ calling on me to die for Him'."

Known as the 'Jerusalem of the East', Wenzhou is reportedly home to the largest Christian community in China and around 1,000 people gathered to form a human blockade against police at Salvation Church on the night of the attack. However, police are said to have used iron batons to beat those who stood in their way, and "bloody pictures and videos of riots" that ensued are now circulating on social networks.

The church is just one of hundreds to be targeted in Zhejiang province – at least 360 have already been completely or partially demolished, apparently as a result of defying building regulations.

Local Christians, however, are convinced that it is part of an invigorated attack against Christianity, which is seen as a rival to the Communist government. ICC reports that local officials "compete" to remove the most church crosses in order to bolster their own careers.

Despite the latest incident of violence, members of Salvation Church are determined to protect their building, and defend their faith.

"We will continue to guard our church cross to the end," one local told ICC.

Sooyoung Kim, ICC Regional Manager for Southeast Asia, has urged the Chinese government to promote the right to religious freedom, which is guaranteed under the nation's constitution.

"Zhejiang provincial authorities have carefully planned and carried out their systematic attack against Christianity and churches. We call on the government of China in the strongest possible terms to immediately stop the anti-church campaign that hurts its own people's heart," she says.

"The world needs a peaceful China that respects human dignity and freedom of religions."

Religious freedom protections are limited to those who worship within state-sanctioned religious bodies in China. Those who choose to practice their faith outside of these, or whose beliefs are not officially recognised by the Government, are at constant risk of being accused of participating in illegal activities, which carries heavy punishment.

However, even those who worship within state-approved 'Three-Self' churches are now facing difficulties, but despite heavy persecution, there are now thought to be 100 million Christians in China – a significant increase from the one million believers when the Communist party came to power in 1949.