Beijing officials have shut down one of Chinas largest "underground" Protestant churches for operating without a licence, the Communist governments latest move to ramp up control over religious worship.
"They chased everyone out and sealed off the place, even tearing down our signage on the wall," Jin told AFP on Monday.
"All our things have been confiscated and we have not been allowed to re-enter the building."
Local authorities said the church and its affiliates have been banned.
"After investigation, (we found) the 'Zion Church in Beijing' was not registered and carried out activities in the name of social organisations without authorisation," the Chaoyang district civil affairs bureau said in a statement.
On Monday, at least a dozen marked police vehicles and scores of officers both in uniform and plainclothes guarded the building where the congregation held its services.
AFP journalists were barred from entering the building. The officers said the third floor was sealed off.
China's officially atheist government is wary of any organised movements outside its own control, including religious ones, and analysts say oversight of such groups has tightened under President Xi Jinping.
The country's Christians are split between those who attend unofficial "house" or "underground" churches and those who go to government-sanctioned places of worship.
"Under Xi, the government has shifted its approach from allowing churches like Zion to operate as long as they don't get political to now seeking to actively control them or shut them down," said Brent Fulton, founder of the ChinaSource website and author of "China's Urban Christians".
Fulton said Jin was probably targeted after he rejected a request by authorities in April to install CCTVs in the sanctuary.
He was among some 200 pastors from underground churches who put their name to a petition complaining of "assault and obstruction" by the government -- including the tearing down of crosses -- since new religious regulations came into effect in February.
Zion was one of the largest "house" churches in Beijing, with up to 1,500 people attending its five weekly services.
"I believe the government will continue to go after high profile unregistered churches... particularly those whose pastors signed the open letter, in order to send a strong signal to other churches," Fulton said, adding that many churches might stop large services and instead have smaller group meetings in homes.
The state-linked China Christian Council estimates the country has around 20 million Christians -- excluding Catholics -- in official churches supervised by the authorities.
But the true number of worshippers could be higher, at least 40 million to 60 million, according to some estimates.
China's roughly 12 million Catholics are divided between a government-run association, whose clergy are chosen by the atheist Communist Party, and an unofficial underground church loyal to the Vatican.
'Sinicization' of religion
China's top leaders have recently called for the "Sinicization" of religious practice -- bringing it in line with "traditional" Chinese values and culture -- sparking concern among rights groups.
The measures increased state supervision of religion in a bid to "block extremism", and in areas with significant Muslim populations, authorities have removed Islamic symbols, such as crescents, from public spaces.
In the far western region of Xinjiang, Uighurs and other Turkic Muslim minorities are harshly punished for violating regulations banning beards and burqas, and even for the possession of unauthorised Korans.
Up to a million minorities are believed to be held in extrajudicial re-education camps in Xinjiang, rights groups say.
"These efforts... have effectively outlawed Islam in the region," said Maya Wang, senior China researcher for Human Rights Watch.
She added that Christians in Zhejiang and Henan have been suppressed, while Hui Muslims in northern Ningxia region have also been put under increased scrutiny.
Asked what he would do going forward, Jin said they would return to the church's location this weekend.
"Longbaochen is our home... even if we can't enter we will go there," he said.
"They can stop us from holding services, but they cannot stop us from praying."