After three days of a free-speech bonanza that included discussions of the ruling Chinese Communist Party's (CCP) genocidal policies in Xinjiang and Tibet, its crackdown on dissent in Hong Kong, and its military threats against democratic Taiwan, China's internet censorship machinery finally cranked into gear and banned the audio chat app Clubhouse.
"The [Clubhouse] app was blocked for users in China around 7.00 p.m. Beijing time [on Monday]," the GreatFire.org website, which monitors Chinese internet censorship, said via its Twitter account.
"The Clubhouse website is still accessible, but the resources that the app needs to access in order to function are blocked," it said.
The block came after the app opened a rare window of opportunity for users in China to speak freely in Clubhouse's moderated audio forums, in Mandarin, and beyond the Great Firewall of government censorship.
Unprecedented conversations were being had on normally banned topics between China-based users, who are fed the CCP's official narrative on most topics for much of the time, and activists in less censored countries, as well as those in democratic Taiwan, Hong Kong and Xinjiang, according to user accounts posted to social media.
News of the ban was greeted with dismay among some Chinese users.
"Walled in, just two days after we got the fire going," commented one user. "So it's a 404 already?" wrote another.
"That was so fast - we were in a group at the time of the ban and got frozen," said another.
A Clubhouse moderator who asked to remain anonymous said China-based users would need some way of circumventing the Great Firewall to join chat forums in the app from now on, and that Chinese government censors would be patrolling Mandarin-language chatrooms with more than 300 participants, and issue warnings to moderators to avoid "sensitive topics."
Li Hengqing, a former student leader in the 1989 democracy protests, said Clubhouse had taken off after Tesla founder Elon Musk had promoted it on social media, but its use had been limited from the outset to iPhone users with phones bought overseas, as Chinese app stores didn't carry it.
'There are concentration camps in Xinjiang'
One of the most groundbreaking chats was titled "There are concentration camps in Xinjiang," during which Mandarin-speakers from around the world shared information about the mass incarceration of at least 1.5 million Uyghurs and other ethnic minorities in "re-education camps," part of a set of CCP policies described as genocide by the U.S. government.
"You can't stop these young people, because they need to break open the Great Firewall, open windows and look out at the world," Li told RFA.
But he said many had been expecting the ban from the start.
"We definitely thought that a total block on Clubhouse was just around the corner," he said. "[But] just last night, around 5,000 people were exposed to the truth [about Xinjiang] ... This was something they couldn't tolerate."
U.S.-based activist Zhou Fengsuo, who founded the rights group Humanitarian China, said he had taken to Clubhouse to talk about his experiences of the 1989 democracy movement on Tiananmen Square, and its brutal suppression in a People's Liberation Army (PLA) killing spree on the night of June 3, 1989 and the days that followed.
"People were cautious when they first joined, but then they would engage very strongly when they saw that so many others shared their views," Zhou said.
"Many people may have been brainwashed, whether its about June 4 or Xinjiang, but the truth is so powerful, that people were able to inspire each other through the collective power of the forum."
"This is what the government fears," said Zhou.
One Clubhouse user from China, who gave only a nickname Alex, said via social media that he had wept for joy several times during the conversation he took part in.
"This is the first time I have come across so many people who speak the same language," Alex said. "We got together and talked about the things I care about the most; stuff that I have never dared to say in Chinese before ... Thank you."
Filtering out Fifty Center Army
As an invitation-only platform, Clubhouse was able to filter out much of the usual interference, insults and online abuse from CCP supporters, known as the Fifty Cent Army.
A black market for invitations sprang up soon after Musk's high profile conversation with RobinHood app president Vlad Tenev was livestreamed on YouTube, with invitation codes changing hands on the auction site Taobao for up to 400 yuan apiece.
By Tuesday, the Taobao listings for Clubhouse invitations had been deleted, and people with China-registered phones were unable to receive invitation codes.
Hong Kong-based users said some had managed to listen in to conversations using a VPN from China.
Shortly before the ban, Chinese political cartoonist Badiucao, who lives in Australia, hosted a chatroom on Clubhouse titled "Has anyone been called in to drink tea over Clubhouse?" in a reference to being called in for questioning by the state security police. As of Feb. 7, it seemed that not many users had.
Former Sina Weibo social media censor Liu Lipeng, who now lives in California, said the authorities were more likely to seek to control Clubhouse activity by blocking it, rather than by retaliating against those who used it.
"This kind of block mostly happens through the Great Firewall, which is a distributed network, so maybe it will still work on some nodes and not on other," Liu said. "But eventually, it won't work at all."
He said there were also security concerns over the fact that the invitations were texted to phones in China, most of which are now registered in the real names of their owners.
"Mobile phone numbers in China all need a real nam, so text messages and verification codes can all be intercepted," he said. "You are very likely to become exposed to your mobile phone service provider."
He said that even if users continued to listen in through VPNs, Chinese government censors are already likely to have infiltrated the chatrooms, and that the use of VPNs by regular users has also been banned.
Reported by Malik Wang and Poon Ka Ching for RFA's Cantonese Service, and by Wang Yun for the Mandarin Service. Translated and edited by Luisetta Mudie.