BEIJING — Chinese authorities detained dozens of pastors from one of the country’s largest underground churches over the weekend, marking the most significant crackdown on Christians since 2018, church officials and relatives said.

Pastor Jin Mingri, founder of the unofficial Zion Church, was taken from his home in Beihai on Friday evening, according to his daughter Grace Jin and church spokesperson Sean Long. Zion Church, which is not sanctioned by the government, has roughly 5,000 regular worshippers across nearly 50 cities.

Around the same time, authorities reportedly detained nearly 30 pastors and church members nationwide, releasing five. About 20 remain in custody. Jin, 56, is being held at Beihai City No. 2 Detention Centre on charges of “illegal use of information networks,” which carries a maximum sentence of seven years.

Grace Jin expressed concern for her father’s health, noting his history of diabetes and restricted access to medication. Lawyers have reportedly been denied meetings with the detained pastors.

The crackdown follows new rules from China’s top religion regulator banning unauthorized online preaching, religious training by clergy, and “foreign collusion.” President Xi Jinping has also called for stricter law enforcement and the further Sinicisation of religion.

Zion Church has grown rapidly, especially during the COVID-19 pandemic, through Zoom sermons and small gatherings. Its growth, observers say, has drawn scrutiny from the Communist Party, which views independent religious networks as a potential threat.

Jin, a Peking University graduate who converted to Christianity after the 1989 Tiananmen crackdown, has previously faced government restrictions, including a 2018 travel ban preventing him from visiting family in the United States. Authorities also detained 11 Zion Church pastors earlier this year.

Sean Long said the crackdown reflects the leadership’s concern over Zion Church’s rapid expansion and well-organized network, which has become increasingly visible in recent years.

U.S. Secretary of State Marco Rubio condemned the detentions, calling for the immediate release of the pastors.