At least 20 Christians are being held in 'black jail' in China, leading to accusations that the government is imposing a "totalitarian regime" on its citizens.

According to Texas-based human rights organisation China Aid, the detained Christians are from the cities of Wenzhou and Jinhua, both in Zhejiang province in the east of the country. They include a number of church pastors and deacons, as well as human rights lawyer Zhang Kai who has been missing since his arrest in August.

Zhang is one of almost 300 human rights lawyers to be arrested in China since July 10, and had represented more than one hundred churches fighting orders to remove their crosses amid a crackdown on places of worship. In July, he wrote and distributed a 'Cross Activists Handbook', advising church leaders on how they can use China's own constitution – which guarantees religious freedom – to defend their rights.

'Black jails' have no legal status, though the official wording states that detainees are being kept under "residential surveillance in a designed location". China Aid has noted that torture is common, and inmates are refused physical, written or verbal communication with family members or legal representatives.

"Where are these people? We don't know, and now most of them have been placed under residential surveillance now instead of criminal detention," an unnamed Christian from Wenzhou told the organisation.

"This is entirely outside the law. These are the actions of totalitarian regimes."

Up to 1,700 churches in Zhejiang have been demolished or had their crosses removed as part of a three-year 'Three Rectifications and One Demolition' campaign, supposedly with the aim of exposing and removing "illegal structures". However, it is widely seen as a move to combat the increasing influence of Christianity in the country.

Another Chinese Christian, identified only by his surname, Wen, told China Aid: "After a year, the cross demolitions had mostly finished. Then came the persecution, as pastors were caught and are still unreleased.

"The officials are becoming more arrogant and more powerful. The thing we need most is to have people who will step up to stop these kinds of things from happening. These people, can we fight for their release?"

The deteriorating human rights situation in China was raised by activists last month as President Xi Jinping made his first state visit to London. Seen as taking a hard-line approach to various parts of civil society, Xi's leadership is cause for significant concern particularly among the religious community, Christian Today was told.

Civil rights activist Chen Guangcheng branded the demolition of church crosses "a public declaration of war to the international religious community".