Twitter's decision to impose a permanent ban on US President Donald Trump's account has sparked some consternation in Europe, with German Chancellor Angela Merkel calling it "problematic".
The move, prompted by fears of "further incitement of violence" after last week's attack on the US Capitol building that was partly blamed on the US president, reignited debate over regulation of social media.
Facebook, Instagram and Snapchat have all now issued their own bans, triggering a flood of reactions from around the world.
Facebook on Monday said they don't have any plan to lift the suspension.
Twitter also announced it has suspended "more than 70,000 accounts" linked to the QAnon conspiracy theory following the attack on the US Capitol.
European commissioner Thierry Breton, who has introduced two EU proposals that would place more restraints on digital giants, saw Twitter's decision as a total break from the past, calling it "the 9/11 moment of social media" in an op-ed published by Politico.
US internet giants have often been accused of holding too much power over social media, and many governments have called for them to face more regulation.
Merkel's spokesman Steffen Seibert said she "considers it problematic that the accounts of the US president have been permanently blocked".
He added: "It is possible to intervene in the freedom of expression, but in accordance with limits defined by the legislator, and not through a decision by company management."
French Economy and Finance Minister Bruno Le Maire agreed, telling state-run France Inter radio: "The regulation of digital giants cannot be done by the digital oligarchy itself."
Russian opposition figure Alexei Navalny also denounced -- on Twitter -- what he branded "an unacceptable act of censorship" based on "emotion and personal political preferences".
Digital law specialist Florence G'sell, calling Twitter's decision an "earthquake", said the social media giants "have greatly profited from the polarisation." He urged for a unfied laws to control them.
US social media have regularly cited Section 230 of the US Communications Decency Act when they claim to simply host accounts but not bear responsibility for the content.