(The Lion) — Thirty Christians were apprehended in China last weekend in one of the “largest arrests in decades,” according to BBC.

The religious persecution has spread across at least 10 cities, including Beijing and Shanghai, targeting one of the largest, most prominent networks of churches in China: Zion Church, BBC reports.

Founded in 2007, Zion Church offers online services, with roughly 10,000 people streaming across more than 40 cities in China, according to International Christian Concern (ICC).

Sean Long, a Zion Church pastor based in the U.S., told the BBC China’s tactic is to scare other churches in China. Long told ICC the “distressing” arrests began Oct. 9 and violate the freedom of religion clause in the Chinese Constitution.

“We want our pastors to be released immediately,” he said.

Despite the persecution, Zion Church continues to meet.

“We will still have online service,” Long said. “We will not stop what we are doing. We will share the good news of Jesus Christ no matter what.”

Pastor Jin Mingri, founder of Zion Church, was arrested Friday Oct. 10, shortly after texting his daughter to inform her of another pastor’s disappearance, BBC reports.

According to an “official detention notice” obtained by BBC, Jin is imprisoned in “the Beihai Number Two prison,” under suspicion of “illegal use of information networks.”

The arrests follow the State Administration for Religious Affairs’ publication of the “Code of Conduct for Religious Clergy on the Internet” in September, ICC reported. The code lists 18 articles of regulation, prohibiting “the online publication of religious content not approved by the government,” according to ICC.

Historically, Christians have endured multiple persecutions under the Chinese Communist Party. In 2016, Chinese leader Xi Jinping called for “the ‘sinicisation’ of religion,” according to BBC. Two years later, the CCP required “government approval for worshipping in public.”

Despite these government crackdowns, millions of Christians reside in China. The Catholic Patriotic Association reports nearly six million Catholics, and the Protestant Three-Self Patriotic Movement records roughly 38 million Protestants. Both these organizations, however, “emphasise loyalty to China and the Communist Party,” according to BBC.

Because of this, many scholars estimate “tens of millions more Chinese” worship at “house churches,” which are unregistered and do not adhere to “state-sanctioned ideologies,” BBC writes.

Corey Jackson, founder of Christian advocacy group Luke Alliance, told the BBC underground churches are preparing for increased persecution and arrests.

U.S. Secretary of State Marco Rubio condemned the arrests in a statement on Oct. 12.

“This crackdown further demonstrates how the CCP exercises hostility towards Christians who reject Party interference in their faith and choose to worship at unregistered house churches,” Rubio said. “We call on the CCP to immediately release the detained church leaders and to allow all people of faith, including members of house churches, to engage in religious activities without fear of retribution.”

Long of Zion Church told the BBC he believes Zion and the underground churches will continue to operate and perhaps even grow.

“Persecution cannot destroy the church,” he said. “If you look back to history, where there is repression, there’s a revival.”