A prominent Chinese pastor who operated outside the Communist Party-recognised Protestant organisation has been sentenced to nine years in prison.

The People's Intermediate Court in the south-western city of Chengdu said Pastor Wang Yi was also convicted of illegal business operations.

As well as the jail term, Wang was fined and had his personal assets seized.

He had led the Early Rain Covenant Church and was arrested a year ago as part of an ongoing crackdown on all unauthorised religious groups in the country.

The government requires that Protestants worship only in churches recognised and regulated by the party-led Three-Self Patriotic Movement.

Even within that framework, the officially atheist ruling party has been seeking to rein in religious expression, including removing crosses from official and unofficial churches.

More widely, the party has demolished places of worship, barred Tibetan children from Buddhist religious studies and incarcerated more than a million members of Islamic ethnic minorities in what are termed "re-education centres".

Early Rain is believed to have had several hundred members who met in different locations around Chengdu, the sprawling capital of Sichuan province.

Many of those were taken from their homes overnight in lightning raids, including Wang's wife, Jiang Rong, who was later released on bail.

Wang had been critical of party head and state president Xi Jinping and made a point of holding a prayer service on June 4 each year to commemorate the 1989 bloody assault on pro-democracy protesters in Beijing's Tiananmen Square.

Beijing's hard line on religion has underscored its contrast with other culturally Chinese societies, such as Hong Kong and Taiwan, where most follow Buddhism and traditional Chinese beliefs, but where Christianity and other religions also thrive.

At least two members of Early Rain fled to Taiwan, the self-governing island democracy that China claims as its own territory.