Twitter and Facebook on Wednesday locked the accounts of President Donald Trump, which prevents him from posting messages to his more than 88 million followers on Twitter and 35 million followers on Facebook, after he published a string of inaccurate and inflammatory tweets on a day of violence in the nation’s capital.

The moves were an unprecedented rebuke of Trump by the social media companies, which have long been megaphones for the president.

Twitter said Trump’s account would remain locked for 12 hours and the ban could be extended if several of his tweets that rejected the election results and appeared to incite violence were not deleted. Trump’s account will be permanently suspended if he continues violating Twitter’s policies against violent threats and election misinformation, the company added.

Twitter said that the risks of keeping Trump’s commentary live on its site had become too high. “Our public interest policy — which has guided our enforcement activity in this area for years — ends where we believe the risk of harm is higher,” a spokesman said.

Facebook later followed by barring Trump from publishing on the social network for 24 hours after finding that he had violated the company’s rules with two posts, a Facebook spokesman said.

The actions followed a torrent of criticism aimed at social media companies for their role in spreading misinformation and being a bullhorn for Trump as a pro-Trump mob stormed the Capitol building Wednesday and halted the certification of Electoral College votes.

For years, Trump had built his influence with posts on Twitter and Facebook. Since losing November’s election, he had used the platforms to challenge the election results and call them fraudulent.

On Twitter on Wednesday, users called for the company’s chief executive, Jack Dorsey, to take down Trump’s account. Civil rights groups said action by social media companies against calls for political violence was “long overdue.” Even venture capitalists who had reaped riches from investing in social media urged Twitter and Facebook to do more.

“For four years you’ve rationalized this terror. Inciting violent treason is not a free speech exercise,” Chris Sacca, a tech investor who had invested in Twitter, wrote to Dorsey and Facebook’s chief executive, Mark Zuckerberg. “If you work at those companies, it’s on you too. Shut it down.”

Twitter, Facebook and others had previously resisted cracking down on Trump’s posts and other toxic content, saying that the posts were in the public’s interest. While the platforms had started taking more steps against political misinformation in the months before the election, they declined to remove Trump’s messages and instead took half measures, such as labelling his posts.

So when violence broke out in Washington on Wednesday, it was, in the minds of longtime critics, the day the chickens came home to roost for the social media companies. After the onslaught of criticism began, Twitter and Facebook started removing several of Trump’s posts from their sites, including one where the president falsely said that “a sacred landslide election victory” had been “unceremoniously & viciously stripped away.”

Facebook, Twitter and YouTube said on Wednesday that they were reviewing the situation and would not tolerate calls for violence on their sites. In a statement, Twitter said it would take action against tweets that violated its policies and was “exploring other escalated enforcement actions”.

YouTube also said on Wednesday that it would not tolerate calls for violence on their sites. The video site said it removed multiple live streams that showed participants storming the Capitol building carrying firearms. It also said it would elevate authoritative news sources on its homepage, in search results and recommendations.

Zuckerberg said in an internal memo to employees that he was “saddened by this mob violence”, according to a copy reviewed by The New York Times. He said Facebook had stepped up the moderation of Trump’s comments because the situation was “an emergency”.

“The peaceful transition of power is critical to the functioning of our democracy and we need our political leaders to lead by example and put the nation first,” Zuckerberg wrote.

Trump also told his supporters to go home in a video that he posted on multiple social media sites Wednesday afternoon. “You have to go home now. We have to have peace. We have to have law and order,” he said while repeating false claims that the election had been stolen from him.