Few things frighten Philip Woo, a pastor and missionary based in Hong Kong. The Lutheran has been spreading his faith among underground churches in mainland China for 25 years.
But since 2013, he has also been engaging in a supposedly less risky activity; organising religious training for Chinese church leaders in the former British colony.
For that, he was summoned to the religious affairs bureau of a district in the southern city of Shenzhen on 1 July, the same day that China enacted a sweeping national security law.
“I was surprised to get the call,” says the 63-year-old. “I had been verbally warned before. That was expected. But this is different. I’m now afraid for my safety when I’m in China.”
At the meeting, the pastor was accused of breaking Chinese law by advertising religious courses to mainlanders on his ministry’s Hong Kong-based website.
He was also verbally instructed to stop preaching to mainland students in Hong Kong.
Although Mr Woo believes he broke no law in the special administrative region, where residents can worship freely, he agreed to sign an official document acknowledging his guilt, in order to protect colleagues who live in China full-time.
Bob Fu, president of the US-based China Aid Association, calls the incident “extraordinary”.
“This is very, very unusual,” says the China-born Christian pastor. “This is the first time I have ever heard of a Chinese religious authority issuing a letter, with a stamp, to a church leader in Hong Kong.”
“It is an escalation of mainland China’s assertiveness over Hong Kong activists. It certainly sets a dangerous precedent.”
Fu, who is best known for advocating on behalf of blind campaigner Chen Guangcheng, says there appears to be a link between the written warning issued to the pastor and a rising number of church closures in Guangdong province, where Shenzhen is located.
According to China Aid, authorities in the province, which borders Hong Kong, have closed, raided or warned more than a dozen unofficial Protestant churches and schools since April.
One of them, the Guangfu House church based in Guangzhou, is trying to sue the government over the forced closure.
Its pastor, Ma Chao, says he has direct knowledge of more than 20 churches in Guangdong that have been asked to close.
He estimates hundreds more churches in the province have received similar orders.
Three Christian schools, including a licensed kindergarten, have also been targeted, he says.
Previously, Guangdong officials had taken a relatively relaxed view of so-called “house churches”, whose members often worship in private homes.
They run independently of the state-sanctioned Three-self Church and China Christian Council, both Protestant groups, and the Chinese Patriotic Catholic Church.
In 2010, the country had some 58 million Protestants and about nine million Catholics in both official and unofficial churches – this was the most recent year for which data is available, according to the Pew Research Centre.
Fu says restrictions on house churches may be lax or tight, depending on their location and the attitudes of local leaders.
Tough provinces include Tibet, Xinjiang, Henan, Guangxi and Anhui.More relaxed regions include Fujian, Shandong, Hebei and until recently, Guangdong. (BBC)