Twitter has shut down more than 200,000 accounts on its platform after discovering a “significant state-backed information operation” linked to the Chinese government targeting pro-democracy protesters in Hong Kong.

There has been widespread unrest in Hong Kong over a now-suspended bill that would have allowed suspects to be extradited to mainland China for trial, with protests now centering on calls for democracy in the region.

In a post about “information operations directed at Hong Kong”, Twitter said it had deleted 936 accounts created by the Chinese government targeting the Hong Kong protest movement.

A further 200,000 accounts found to be part of a “larger, spammy network” were also “proactively suspended” by Twitter before they were able to be active on the platform.

“Overall, these accounts were deliberately and specifically attempting to sow political discord in Hong Kong, including undermining the legitimacy and political positions of the protest movement on the ground,” Twitter said in the statement.

“Based on our extensive investigations, we have reliable evidence to support that this is a coordinated state-backed operation. Specifically, we identified large clusters of accounts behaving in a coordinated manner to amplify messages related to the Hong Kong protests.”

The accounts were deleted and suspended for a range of violations of Twitter’s terms of use, including for spam, coordinated activity, fake accounts, attributed activity and ban evasion.

Twitter also provided examples of the accounts that had been deleted and some of the tweets made by them.

“Those people with ulterior motives indicated by forces hide behind the scenes laid siege to the legislative,” one post said. “The path of your darkness and the bright roads of the masses of the Hong Kong people will not inevitably coexist.”

Source: Twitter

“It’s a complete violent behaviour, we don’t want you radical people in Hong Kong. Just get out of here!” another posted.

This sort of state-backed behaviour “violates the fundamental principles” on which Twitter is built.

“We will continue to be vigilant, learning from this network and proactively enforcing our policies to serve the public conversation,” the social media company said.

“We hope that by being transparent and open we will empower further learning and public understanding of these nefarious tactics.”

Twitter also tipped off its social media rival Facebook about the prevalence of China-backed accounts. In a later post, Facebook said it had removed seven pages, three groups and five accounts it found to be involved in “coordinated inauthentic behaviour as part of a small network that originated in China and focused on Hong Kong”.

“The individuals behind this campaign engaged in a number of deceptive tactics, including the use of fake accounts to manage pages posing as news organisations, post in groups, disseminate their content, and also drive people to off-platform news sites,” Facebook said in a statement.

Facebook’s investigation found the accounts to be linked to individuals associated with the Chinese government. The accounts in question had 15,500 followers, and 2,200 accounts had joined at least one of the now-deleted groups.

“We are making progress rooting out this abuse, but as we’ve said before, it’s an ongoing challenge,” Facebook said.

“We’re committed to continually improving to stay ahead. That means building better technology, hiring more people and working more closely with law enforcement, security experts and other companies.”