Christian Solidarity Worldwide has voiced concerns over reports of a crackdown on unregistered Christian meetings in China's Xinjiang province.
It was responding to reports from China Aid Association warning that in the last five months, a number of groups have been closed down, fined or had members detained by the police.
Most of the meetings had fewer than 20 people and were taking place in a private residence.
A group in Yili was closed down by the authorities and in Kurla, police armed with guns and electric batons searched a house that was being used for church meetings, with one woman being detained.
In June, police and security officials interrupted two meetings in Urumqi, with two members being detained. Another meeting was interrupted in August and one of them was taken in for a second time. He has filed for administrative reconsideration in a bid to stop the interference.
CSW says that in a majority of cases, the officials failed to show identification or a warrant for the searches.
The Chinese government permits Christian activities in state approved churches but unregistered churches are considered illegal.
In Xinjiang there are greater restrictions on civil and political rights, with even registered religious activities being closely monitored, CSW said.
CSW's Chief Executive Mervyn Thomas said, "We are very concerned about restrictions on peaceful meetings of Christians and other religious minorities in Xinjiang. By prohibiting even small-scale, private religious activities, the government is severely restricting individuals' right to freedom of religion or belief.
"Furthermore, the fact that, in many cases, police and security officers do not show any identification or warrant reflects the general weakness in rule of law in the region.
"We urge the Chinese government and Xinjiang local government to protect the right of all religious minorities to freedom of religion or belief, and to allow those who believe they have been wrongfully detained to file for administrative reconsideration."