Under orders from Beijing, authorities in the coastal city of Wenzhou found in a two-month inspection that only 3,200 of the area's 8,000 religious sites were properly registered, the Hong Kong-based Information Center for Human Rights and Democracy reported.
So far, of the nearly 4,800 illegal sites, 3,011 have been closed or torn down, the group said, citing sources it did not identify.
Among the illegal sites, more than 400 were Protestant and Catholic churches, while the rest were Buddhist, Taoist and local religious temples and shrines, the group said. It added that the legal places of worship included 1,200 Protestant and 120 Catholic churches.
The report was released after business hours and could not be immediately confirmed. Wenzhou government offices were closed and duty officers declined comment.
But earlier this month, when the clampdown was first reported, local officials confirmed 450 buildings were destroyed to suppress what they called rampant superstition.
The Information Center said that the increased numbers of shutdowns showed the campaign was accelerating.
The numbers of religious sites underscored Wenzhou's reputation as a flourishing center for religion in China, where the communist government espouses atheism. The area, comprising two cities and six counties, has 7.2 million people - 1.3 million of whom profess religious belief, the center said.
China recognizes only five religions -- including Christianity (which it subdivides into Catholcism and Protestantism), Buddhism, Islam and Taoism -- and has tried to control the numbers of believers through restrictions on worship and bans on proselytizing.
Belief in religion and health sects has soared in recent decades as social controls loosened and market reforms discredited communist ideology.