An influential Protestant church in China says 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 is 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.

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.

Li and his wife Zhang Xinyue are among the four who remain in detention. Their church described the arrests as a concerted operation but said the grounds for arrest, and whether those detained have been charged, remain unclear. It added that it had lost contact with two other members but did not say they had been detained.

The situation is ongoing, with specific details yet to be fully confirmed, Early Rain Covenant Church (ERCC) said in a statement to members and supporters. It also sought prayers for its members' safety and their perseverance in the Christian faith.

In Wenzhou, local authorities brought in bulldozers, cranes and heavy machinery earlier this week and started taking down part of the Yayang Church building. ChinaAid said it was told by multiple sources that hundreds of armed and special police officers have been deployed to stand guard outside the building.

The massive mobilisation against the two major independent church networks shows the central government is determined to stamp out Christian churches entirely, unless the church is totally indoctrinated into the party's ideology, said Bob Fu, who founded ChinaAid.

In December, authorities arrested about 100 members of Yayang Church in Wenzhou over five days. At least 24 members remain in custody, according to Human Rights Watch. The Chinese government has also targeted the Early Rain Covenant Church, founded in 2008, for years. In 2018, authorities raided the church and arrested founding pastor Wang Yi and his wife Jiang Rong. At least 100 church members were taken into custody in the following days in one of China's largest crackdowns on churches in the past decade.

Xi Jinping's government has tightened ideological control and intensified its intolerance of loyalties beyond the Chinese Communist Party, said Yalkun Uluyol, China researcher at Human Rights Watch.

Concerned governments and religious leaders around the world should press the Chinese government to free detained religious adherents and respect religious freedom in China, Uluyol added.