According to Christian religious freedom charity China Aid, they interrupted the church's service in the Ningxia region and told worshippers that they had conducted religious activities in a non-government approved building, which was illegal.
The person that led the service, Lou Siping, told the charity: "After their arrival, they first asked 30 of us to take out our ID cards and register them. We cooperated and registered them. Then, the police took us to the station for investigation.
"They said our church did not go to the National Religious Affairs Bureau to register, violating the regulations, and must be stopped immediately."
Siping said he reminded the investigators about China's Constitution which promises religious freedom, but said he was repeatedly told that they gathered unlawfully.
Authorities also contacted the church's landlord and demanded the cancellation of the church's lease.
China Aid said the Christians were threatened with coercive measures if they fail to vacate the building the next day.
It's been reported that officials also ordered that the church to join the Three-Self Patriotic Movement, a Christian offshoot of the government that allows authorities to police church services.
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