Facebook and Twitter are cracking down on what they say is a China-backed disinformation campaign to "undermine" ongoing protests in Hong Kong.
Huge demonstrations have been staged in the former British territory in recent months over proposed legislation that would allow authorities to detain and extradite people wanted in countries Hong Kong did not already have agreement with, including mainland China.
Although the controversial bill has since been suspended, a refusal to completely withdraw it has seen the protests continue and escalate – with organisers estimating that at least 1.7 million took part in a rally on Sunday.
China has been heavily critical of the demonstrations, and Facebook and Twitter have revealed that they are working to block efforts from within the country to "undermine" the movement through disinformation – which the latter said was an attempt to "sow political discord in Hong Kong".
Twitter announced that it had removed 936 accounts that were "behaving in a co-ordinated manner to amplify messages related to the Hong Kong protests", with Facebook removing five accounts, seven pages and three groups it said were engaged in "a number of deceptive tactics".
Both social networks are blocked in China and Twitter said many of the accounts it had banned were accessing the platform via a virtual private network (VPN), which allows users to bypass such restrictions.
Others were able to tweet "from specific unblocked IP addresses originating in mainland China".
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Twitter said the accounts it had banned were "the most active portions" of a "co-ordinated state-backed operation" that involved some 200,000 profiles, many of which have been created since the suspensions.
It added: "We will continue to be vigilant, learning from this network and proactively enforcing our policies to serve the public conversation. We hope that by being transparent and open we will empower further learning and public understanding of these nefarious tactics."