Twitter announced Monday that it would no longer accept advertising from "state-controlled news media entities" after finding that more than 900 accounts originating from inside China have been part of a coordinated effort to undermine political protests in Hong Kong.The big picture: Hong Kong saw its 11th straight week of pro-democracy protests over the weekend as the city pushes back on what it views as encroachment by the Chinese government on its autonomy. The accounts, which Twitter said were part of a "coordinated state-backed operation," sought to delegitimize the protest movement.Twitter is currently banned in mainland China. The platform says most of the accounts gained access through VPNs.The social network says the account violated its platform manipulation policies, which prohibit spam, coordinated activity, fake accounts and ban evasion. Per BuzzFeed News' Ryan Mac, "tax-payer-backed entities with independent oversight like the BBC, CBC, and NPR" will still be allowed to run ads on Twitter.Facebook also said Monday that it removed 7 pages, 3 groups and 4 accounts "involved in coordinated inauthentic behavior as part of a small network that originated in China and focused on Hong Kong."Our thought bubble, per Axios' Sara Fischer: Coordinated misinformation campaigns have often been used by governing bodies against their own populations. Twitter found examples of this with Saudi Arabia's government last year, and Facebook found examples in Myanmar as well.Go deeper: Pence suggests Hong Kong clampdown could prevent China trade deal