Violent supporters of President Donald Trump have breached the Capitol in Washington, as lawmakers met to confirm president-elect Joe Biden's poll win.
Pro-Trump rioters clashed with security officials and stormed the building on Wednesday afternoon during what is usually a straightforward ceremonial procedure.
President-elect Biden called on Trump to go on national television to "fulfill his oath, defend the Constitution and demand an end to this siege."
Adding that it was an "insurrection".
Mr Trump released a video message asking supporters to go home and later deleted it.
Mr Trump also tweeted calling for calm after the violence escalated inside the building. He wrote: “I am asking for everyone at the US Capitol to remain peaceful. No violence!”
“Remember, WE are the Party of Law & Order – respect the Law and our great men and women in Blue,” he added. “Thank you!”
The joint session of Congress certifying Mr Biden's win has been suspended and forced into recess.
There are reports of guns drawn in the building and at least one person, a woman was shot. She was reported to be in a critical condition but died shortly after arriving at the hospital. Several police were also injured.
There were also reports of armed confrontation at the doors of the House of Representatives. Tear gas was also used.
Nearly an hour after the recess, photos emerged online of the rioters having entered the chambers, with one screaming about Mr Trump’s electoral defeat from the dais and falsely claiming he won.
Rioters were seen marching through the building chanting "We want Trump" and one was photographed in the Senate president's chair.
The doors of the Senate were closed and locked, and senators were told to stay away from the area. The doors to the House were barricaded, and some lawmakers were seen praying.
Senator Majority Leader Mitch McConnell broke from Donald Trump, strongly rebuking the president's attempt to overturn the 2020 presidential election loss using "sweeping conspiracy theories."
"If this election were overturned by mere allegations from the losing side, our democracy would enter a death spiral. We'd never see the whole nation accept an election again," McConnell said.
The latest reports say the steps of the Capitol have now been cleared. But there is little sign that the protesters are obeying 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).
Twitter and other social media channels were flooded with images of protesters skirmishing with police officers, and there were multiple reports of rioting inside the Capitol as some rioters broke windows, battered down doors and postured in the Senate chamber.
Five weapons were recovered from the complex, and around 13 arrests were made, D.C. police said. None of the people were residents of the district.
For days Mr Trump had been putting pressure on Mr Pence, who is presiding over the session, to block certification of the result.
However, in a letter to Congress on Wednesday, Mr Pence said that he had no "unilateral authority to decide which electoral votes should be counted".
Mr Trump, who has called the protesters "patriots", has refused to concede the 3 November election, repeatedly alleging fraud without providing any evidence.
On Wednesday, he said again: "We will never give up. We will never concede."
Republician Ilhan Omar, D-Minn., tweeted that she was drawing up articles of impeachment against Trump.
"We can’t allow him to remain in office, it’s a matter of preserving our Republic and we need to fulfill our oath," she tweeted.
Trump was initially impeached by the House in late 2019 and acquitted by the Senate in early 2020.
Meanwhile, political figures across the world expressed shock. UK Prime Minister Boris Johnson condemned "disgraceful scenes" and called for a "peaceful and orderly transfer of power".