President Donald Trump’s supporters stormed a session of Congress held Wednesday to certify Joe Biden’s election win, triggering unprecedented chaos and violence at the heart of American democracy and accusations Trump was attempting a coup.

Pledging not to be deterred, legislators resumed business after dark and the Senate soundly rejected the first of several expected challenges to Biden’s win, with several Trump loyalists reversing course in the wake of the violence that drew condemnation around the world.

Egged on to an extraordinary rally across town by an aggrieved Trump, a flag-waving mob broke down barricades outside the Capitol and swarmed inside, rampaging through offices and onto the usually solemn legislative floors.

Four people died and 52 were arrested as supporters of Trump violently occupied the US Capitol in Washington, DC, Police Chief Robert Contee said during a late night press conference.

The dead included a woman who was shot by the US Capitol Police and one adult female and two adult males who died in “medical emergencies”, Contee said.

One Trump backer in jeans and a baseball cap was pictured propping a leg up on House Speaker Nancy Pelosi’s desk, where a threatening note had been left, as throngs of others climbed onto risers set up for Biden’s inauguration on January 20, holding a banner that read: “We the people will bring DC to its knees/We have the power.”

Biden called the violence an “insurrection” and demanded that Trump immediately go on national television to tell the rioters to leave.

“Our democracy’s under unprecedented assault,” Biden said in his home state of Delaware.

“This is not dissent. It’s disorder. It’s chaos. It borders on sedition. And it must end now.”

Trump soon afterward released a video in which he called on the mob to leave but stood by his unfounded claims of election fraud.

“We have to have peace. So go home. We love you — you’re very special,” he said.

In a major step, social media companies pulled down Trump’s video on accusations it aggravated violence and Twitter temporarily suspended his account, warning the tweet-loving tycoon he faces a permanent ban if he does not conform to rules on civic integrity.