The authorities in China have arrested 12 members of an underground Christian church, officials said on Thursday.
At least eight of those arrested face imprisonment in a labour camp on charges of engaging in "feudalistic superstition".
A US-based group, Human Rights in China (HRIC), has criticised the move, accusing Beijing of engaging in relentless persecution of religious freedom.
The group has asked for the detainees to be released immediately.
The arrests, which took place two weeks ago in Funing County in the south-western province of Yunnan, are part of a continuing crackdown on churches operating out of private homes in the country.
Although Chinese law recognises religious freedom, the Communist authorities ban all religious activities which are not officially endorsed by the government.
According to the HRIC, the church concerned had been applying for permission to hold services for some time.
But on 6 June, town officials turned up at the four locations
where the church was holding services, and arrested 12 of the worshippers.
A government official told the BBC that eight of the detainees had been sent for re-education through labour, effectively a prison sentence that under Chinese law requires no trial.
Millions of Chinese are thought to worship at unofficial Christian 'house churches' throughout the country.
Nicolas Bicquelin, HRIC research director, told BBC News Online that the number of house churches had grown markedly in the last decade, because adherents wanted to worship according to how they felt, rather than in a state-sanctioned manner.
Christian evangelists are very active in some parts of the country, and in certain areas the government tolerates their presence.
But BBC correspondent Adam Brookes says that, in general, the state is wary of any movement that exists outside of its control, and is particularly suspicious of aggressive evangelising.
Liu Qing, the HRIC president, said that under international agreements which China had signed, its citizens should be guaranteed freedom of religion.
"That includes the right to worship in the privacy of one's home as much as the right to worship publicly in a church," Mr Liu said in a statement.
"Labelling this worship as engaging in feudalistic superstition
does not excuse the Chinese authorities' relentless persecution of
people exercising basic human rights," he said.