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

Bob Fu of the U.S.-based group China Aid said over the weekend that the closure of churches in central Henan province and a prominent house church in Beijing in recent weeks represents a "significant escalation" of the crackdown.

"The international community should be alarmed and outraged for this blatant violation of freedom of religion and belief," he wrote in an email.