Members of Early Rain Church in Sichuan have been prevented from meeting following a number of arrests including the church leader pastor Wang Yi and his wife Jiang Rong on 9th December.
Both have been charged with state subversion.
An estimated 23 people have been detained or are missing since the arrests were made last month.
Bulletins posted on social media reported that the church's WeChat groups and over half the personal WeChat accounts of church members had been closed down or restricted from sending messages since the crackdown began.
Between 20th and 31st December, authorities closed churches and confiscated materials from unregistered church groups in Anhui, Inner Mongolia and elsewhere in Sichuan, and prevented or interrupted Christmas celebrations in many places across the country.
School children were warned not to participate in Christmas events and there were reports in several cities of restrictions on Christmas decorations in public places.
Religious freedom charity Christian Solidarity Worldwide's chief executive Mervyn Thomas CMG said: "We are alarmed by the deterioration in the level of freedom of religion or belief in China, not only during the Christmas period but in 2018 overall.
"The forced closure of places of worship, and the detention of citizens peacefully gathering for religious services, suggest a dangerous direction for religious freedom in China. We call on the authorities to end the practice of using 'national security' as justification for detaining religious adherents and those who defend the right to freedom of religion or belief.
"We further call on the authorities to cease the forced closure and demolition of places of worship, and to release all those detained in connection with their beliefs or their defence of human rights, including Wang Quanzhang, Wang Yi and members of Early Rain Church, and all those arbitrarily detained in Xinjiang."
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