Twitter has removed more than 900 accounts it said originated in mainland China to “sow political discord” in Hong Kong, where pro-democracy protests have been ongoing for weeks.

In total, the social media site said Monday it took down 936 accounts, which were “the most active portions” of a larger network of around 200,000 suspended accounts.

“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 a blog post Monday. “Based on our intensive investigations, we have reliable evidence to support that this is a coordinated state-backed operation.”

Facebook also announced Monday that it had identified a similar pattern and removed five accounts, three groups and seven pages that reached as many as 15,500 users.

“Although the people behind this activity attempted to conceal their identities, our investigation found links to individuals associated with the Chinese government,” wrote Nathaniel Gleicher, Facebook’s head of cybersecurity policy in a blog post.

Both sites shared screenshots of posts made by suspended accounts. In multiple examples, protesters were called “thugs” and “cockroaches” and compared to ISIS fighters.

While the social media sites are blocked in China, the banned accounts managed to access them using VPNs (virtual private networks sometimes used to get around blocked web pages) and direct content to users in Hong Kong.

Twitter also said it plans to stop accepting ads from “state-controlled news media entities.” Such accounts devoted exclusively to entertainment, sports or travel content will not be affected, unless such content is mixed with news, the company added.

“This policy will not apply to taxpayer-funded entities, including independent public broadcasters,” the company said in a separate blog post Monday.