Lawmakers have returned to the US Capitol to finish certifying Joe Biden’s election victory, hours after Trump supporters stormed the building in a riot that saw four people die.
Officials say one woman was shot by police, while three others died as a result of “medical emergencies”.
The pro-Trump mob stormed the building in a bid to overturn the election result, suspending a Congress session.
US President-elect Joe Biden blasted the “insurrection”.
President Donald Trump, who had urged the demonstrators to march on the Capitol, later called on them to “go home”, while continuing to make false claims of electoral fraud.
Twitter and Facebook later froze his social media accounts.
US Vice-President Mike Pence started the resumed session on Wednesday evening, in which lawmakers are counting and confirming electoral votes, saying it had been a “dark day in the history of the United States Capitol”.
Some Republicans are raising objections in the session in an effort to overturn the result – a bid that is all but certain to fail.
The rampage on Wednesday came as two Democrats won Senate seats in elections in Georgia, which shifted the balance of Congress to their party’s effective political control, aiding the passage of Mr Biden’s agenda after he is inaugurated on 20 January.
What do we know about the deaths?
Officials say four people died during the storming of the Capitol building.
One woman was shot by police, while three others died as a result of unspecified “medical emergencies”.
Mayor Murial Bowser said the woman who was shot was part of a group of individuals that forced entry into the House room, which was still in session. They were confronted by plainclothes officers, and an officer pulled out a weapon and fired it, she said.
The woman was taken to hospital and proclaimed dead. She has not been officially named, but local media identified her as San Diego-area US Air Force veteran and Trump supporter Ashli Babbit.
Officials said the three other deaths included one woman and two men. Further details of how they died have not been made public.
At least 14 members of the police were injured during the unrest.
What happened at the Capitol?
Protesters surged up the Capitol steps at about 14:15 local time (19:15 GMT), shoving past barricades and officers in riot gear to penetrate the building.
The action was targeting the joint session of Congress being held to certify Mr Biden’s election victory on 3 November.
The invasion sent members of Congress scrambling for cover under their seats as tear gas was fired.
The mob – some of whom wore body armour – used chemical irritants to attack police, according to Washington Metropolitan Police Chief Robert Contee.
They shouted and waved pro-Trump and US flags as they roamed the halls, demanding the results of the presidential election be overturned.
Several thousand National Guard troops, FBI agents and US Secret Service were deployed to help overwhelmed Capitol police.
Federal law enforcement officials said two suspected explosive devices were found and were both rendered safe by the FBI and Capitol Hill police. Washington DC Metropolitan Police said five guns were seized.
The occupation lasted more than three hours before the building was secured by law enforcement. But there was little sign the protesters were heeding Mr Trump’s call to go home, despite a citywide curfew declared by the city mayor from 18:00 to 06:00 (23:00 to 11:00 GMT).
So far, more than 52 people have been arrested – 47 of them for curfew violations.
There were also protests on Wednesday at state legislatures in Kansas, Georgia, Utah and on the other side of the country in Oregon and the north-western state of Washington.
How did Biden and Trump react?
Democrat Mr Biden, who defeated the Republican president in November’s White House election, said the protesters’ activity “borders on sedition”.
He also said democracy was “under unprecedented assault”.
“To storm the Capitol, to smash windows, to occupy offices on the floor of the United States Senate, rummaging through desks, on the House of Representatives, threatening the safety of duly elected officials. It’s not protest; it’s insurrection.”
Mr Trump, meanwhile, responded to the action in a recorded video on Twitter, repeating his unproven claims of election fraud.
“I know your pain. I know you’re hurt,” he said.
“We had an election that was stolen from us. It was a landslide election, and everyone knows it, especially the other side.
“But you have to go home now. We have to have peace.”
For the first time, Twitter froze Mr Trump’s account. The social media company announced it would keep the account locked for 12 hours, demanding he delete three tweets that it said could stoke violence and threatening “permanent suspension”. Facebook and Instagram followed suit.
Earlier on Wednesday, Mr Trump addressed a “Save America Rally” outside the White House.
He had urged supporters to head to the Capitol and said: “Our country has had enough and we will not take it anymore.”
Political figures across the world condemned the storming of the US Capitol.
Former President Barack Obama said in a statement that history would rightly remember the assault on the Capitol as “as a moment of great dishonour and shame for our nation”.
And former US President George W Bush said in a statement: “It is a sickening & heartbreaking sight. This is how election results are disputed in a banana republic – not our democratic republic.”
What has been happening in Congress?
The two houses of Congress – the House of Representatives and the Senate – are counting and certifying the Electoral College votes from the US’s 50 states. Mr Biden received 306 votes to Mr Trump’s 232.
The proceedings are usually brief and ceremonial but Republican lawmakers have been objecting to some results.
So far, the House and Senate have rejected an objection to Mr Biden’s win in Arizona.
For days Mr Trump had been piling pressure on his vice-president, who was presiding over the session, to block certification of the result. But in a letter to Congress on Wednesday, Mr Pence said that he had no “unilateral authority to decide which electoral votes should be counted”.
Senate Republican leader Mitch McConnell also definitively broke with Mr Trump in an emotional speech from the chamber floor.
The Kentucky senator warned: “If this election were overturned by mere allegations from the losing side, our democracy would enter a death spiral.”
After the session resumed, Senate Democratic leader Chuck Schumer blasted the mob at the Capitol as “rioters and insurrectionists, goons and thugs, domestic terrorists”.
He said the president “bears a great deal of the blame”.
Senator Kelly Loeffler, who lost her bid for election in Georgia’s vote on Tuesday, said she could no longer in good conscience vote against certification as she had originally planned, citing the “abhorrent” invasion of the Capitol.