PALO ALTO, U.S./HONG KONG -- Social media is the new front in the clash between Hong Kong protesters and the Chinese government, with Facebook and Twitter accusing Beijing of coordinating a campaign to discredit the activists.
A meme posted on Facebook early this month juxtaposed pictures of Hong Kong protesters and Islamic State terrorists. The question "what's the difference?" was splashed across the image.
This was among the posts cited by Facebook on Monday when it announced the removal of a total of 15 accounts, pages and groups involved in "coordinated inauthentic behavior" focused on Hong Kong, with apparent links to "individuals associated with the Chinese government."
On the same day, Twitter said it had suspended 936 accounts suspected of "deliberately and specifically attempting to sow political discord in Hong Kong" in a "coordinated state-backed operation," along with another 200,000 accounts shut down before they were "substantially active."
This appears to be the first time that American social media companies have specifically called out the Chinese government for meddling on their platforms, and the move has riled Beijing and its supporters.
"The takedown campaign, which is an arbitrary crackdown of different voices, is a violation of freedom of speech," China University of Political Science and Law professor Zhu Wei told the Communist Party-run Global Times.
Also on Monday, Twitter announced it would stop accepting ads from state-controlled media. The move followed reports that China's state-run Xinhua News Agency had bought ads featuring videos expressing support for Hong Kong police in their crackdown on the demonstrations.
Asked Tuesday about the policy change, Chinese Foreign Ministry spokesperson Geng Shuang defended the posts. "It is just understandable that Chinese media use overseas social media to elaborate on China's policy and tell China's story and interact with local people," he told reporters.
"I wonder why certain companies or people would have such strong reactions," he said. "Did it somehow hit their soft spot?"
Pro-Beijing internet trolls -- disparagingly nicknamed the wumao, or "50 Cent," army after the amount they are said to be paid for each post -- are believed to be involved in the anti-protest messaging. Though American social media platforms are blocked in mainland China, the wumao can post comments supportive of the government in hopes of nudging public opinion abroad.
The occupation of the Hong Kong Legislative Council chamber, and a later incident in which protesters attacked a journalist from the Global Times, each touched off a deluge of online condemnation, much of which likely came from wumao.
The Chinese government itself has also used its censorship powers to keep a tight rein on information reaching the mainland. Users of the Weibo microblogging service -- China's equivalent to Twitter -- are restricted from viewing posts with expressions of support for the protesters, but criticism of pro-democracy activism is fair game.
The demonstrators have also turned online communications channels to their advantage. Social media is a vital tool for the leaderless movement to disseminate important information and get their message out. Protesters use the iPhone's AirDrop feature -- a medium authorities cannot control -- to share images of apparent police brutality and shape public opinion.
Social media also helped spread the story of a young woman shot in the eye, allegedly by police. She became a symbol of the movement, with gained momentum leading to the shutdown of Hong Kong International Airport.
When communicating online, many young Hong Kongers look to stay under the mainland's radar by using phonetic spellings of Cantonese, a variety of Chinese widely spoken in Hong Kong that is difficult for speakers of standard Mandarin to understand.
By calling out an apparent manipulation effort by Beijing, Twitter and Facebook are trying to regain some of the trust they lost by failing to address meddling on their platforms by Russia ahead of the 2016 U.S. presidential election. Both companies have come under heavy fire from the public and American lawmakers over their inadequate response, and calls are growing for the government to regulate them more tightly or even break them up.
"Covert, manipulative behaviors have no place on our service," Twitter wrote Monday.
Before the move against the Chinese network, Facebook and Twitter removed accounts linked to the Saudi, Iranian and Russian governments. As the 2020 U.S. election approaches, they are on high alert for interference that could give their critics more ammunition.
Taiwan's presidential election, which is coming up in January, is likely to present a challenge as well. Beijing is keen to avoid the reelection of pro-U.S. incumbent Tsai Ing-wen, and the wumao could jump back into service.