An influential Protestant church in China reports that prominent leaders were arrested in what appears to be a growing crackdown on the underground church movement.

Nine people were detained on Tuesday after police raided their homes and the church office in Chengdu, the Early Rain Covenant Church said. Five of them had been released by Wednesday.

More than 1,000 miles away in Wenzhou, authorities began demolishing the Yayang Church building, as seen in video obtained by the non-profit ChinaAid, which monitors religious persecution.

This latest wave of arrests, after others last year, shows the Communist Party's resolve to snuff out churches that do not align with its ideology, Christian groups say.

The BBC has contacted China's embassy in the UK for comment. Authorities have not made any statements about the arrests or the demolition in Wenzhou.

China promotes atheism and controls religion. The government said in 2018 there are 44 million Christians in the country, but it's unclear if that number includes those who attend the many underground churches.

The Party has long pressured Christians to join only state-sanctioned churches led by government-approved pastors. However, Christian groups say the grip has tightened noticeably, with arrests becoming more common and prompt.

Just weeks ago, Li Yingqiang, the current leader of Early Rain Covenant Church, had said he sensed a storm gathering and referred to the imminent prospect of... another large-scale crackdown.

The church described the arrests as a concerted operation but stated that the grounds for arrest, and whether those detained have been charged, remain unclear. It also added that it had lost contact with two other members.

In Wenzhou, local authorities brought in bulldozers, cranes, and heavy machinery earlier this week, starting to take down part of the Yayang Church building. Reports indicate that hundreds of armed and special police officers have been deployed outside the building.

The crackdown has raised alarms among human rights groups, who see this as a blatant effort to stamp out Christian churches unless they are fully indoctrinated into the Party’s ideology.

Authorities previously arrested around 100 members of Yayang Church in December, and earlier crackdowns had seen substantial detentions and ongoing governmental pressure on prominent church leaders.

Under Xi Jinping's government, China has ramped up its control over religious freedoms, with ideologies requiring conformity to Chinese culture and values increasing. Analysts predict that without international intervention, the situation for religious adherents, particularly within the underground Christian community, will continue to deteriorate.