Supporters of US President Donald Trump enter the US Capitol to protest the election results. — AFP/VNA Photo

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

Moments after an extraordinary rally by Trump seeking to overturn the election, a flag-waving mob broke down barricades outside the Capitol and swarmed inside, rampaging through offices and onto the usually solemn legislative floors.

One woman died in unclear circumstances after being shot inside the Capitolt and others were injured, police said, with lawmakers evacuated and handed protective masks as police fired tear gas.

One Trump supporter 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 urge his supporters to lift the siege of the Capitol.

"Our democracy's under unprecedented assault," Biden said in his home state of Delaware.

"The scenes of chaos at the Capitol do not reflect a true America," he added.

"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 his supporters 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 rare step, social media companies restricted or pulled down the president's video, saying it could encourage violence.

Authorities said they succeeded in clearing out the Capitol of rioters after around four hours but hundreds of Trump supporters remained outside, defying a 6pm (2300 GMT) curfew imposed across the city by Mayor Muriel Bowser.

Sonya Fitzgerald, a 43-year-old Trump supporter from Florida, said on the Capitol steps: "You'll hear about this in the history books."

‘Inciting a coup'

The chaos at the Capitol came a day after Biden enjoyed a new triumph, with his Democratic Party projected to win two Senate runoff seats, handing them full control of Congress.

Historians said it was the first time that the Capitol had been taken over since 1814 when the British burned it during the War of 1812.

For more than two centuries, the joint session of Congress has been a quiet, ceremonial event that formally certifies the election winner -- but

Trump urged members of his Republican Party to reject the outcome.

"The President of the United States is inciting a coup. We will not be intimidated. We will not be deterred," tweeted Democratic Representative Karen Bass, in words echoed by multiple lawmakers.

Former president George W. Bush tacitly denounced fellow Republican lawmakers for their "reckless behavior" and said, "This is how election results are disputed in a banana republic -- not our democratic republic."

US allies also voiced shock, with British Prime Minister Boris Johnson denouncing the "disgraceful scenes" and German Foreign Minister Heiko Maas urging Trump backers to "stop trampling on democracy."

‘Damage our republic forever'

Pelosi announced that Congress would resume its session later on Wednesday, showing it would not be cowed by the violence.

Biden is certain to become president, with Democrats already controlling the House of Representatives, but more than 140 Republican House members and a dozen Republican senators have sided with Trump in challenging the results even though no evidence of fraud has been proven in court.

Republican Senate leader Senator Mitch McConnell, closely aligned with Trump throughout his presidency, denounced the challenge in an impassioned address, noting that the results were not even close.

"The voters, the courts and the states have all spoken. If we overrule them, it will damage our republic forever," said McConnell, who is set to lose his position of majority leader after Democrats' Senate wins.

"If this election were overturned by mere allegations from the losing side, our democracy would enter a death spiral," said McConnell, who also accused Democrats of not accepting Trump's surprise 2016 victory.

Senator Chuck Schumer voiced alarm moments before protesters entered the Capitol, saying: "An element of the Republican Party believes their political viability hinges on the endorsement of an attempted coup."

But Senator Ted Cruz, a Republican, pushed against Biden's certification by saying that many Americans did not accept the election results and needed an investigation.

"I would urge to both sides perhaps a bit less certitude and a bit more recognition that we are gathered at a time when democracy is in crisis," Cruz said shortly before the violence.

Trump had urged his supporters to march to the Capitol in an angry, gambling speech outside the White House.

Trump warned "weak" Republicans not to certify Biden's victory and put direct pressure on Vice President Mike Pence, who ceremonially presided over the session.

"We will never give up. We will never concede," Trump told the cheering crowd, few wearing masks despite a spike in Covid-19 cases.

"I hope Mike has the courage to do what he has to do."

As Trump was still speaking and Congress opened the session, Pence -- dutifully loyal to Trump for four years and quiet since the election -- said he not believe he had authority to intervene.

Pence was rushed out of the Capitol and in a statement urged Trump's supporters -- some of whom have begun chanting against him -- to "stop now."

Thousands of Trump supporters headed to Washington at his urging in recent days, with downtown businesses boarding up in fear of violence.

"I can't say I respect our election process anymore," said Gail Shaw, 76, who drove down from New Jersey. "We will take our nation back."

Biden won in excess of seven million votes more than Trump in the November 3 election and leads him 306-232 in the state-by-state Electoral College count that determines elections, with Republicans unable to prove in court a single allegation of fraud.

New mandate for Democrats

The session of Congress comes one day after voters in Georgia apparently handed a pair of stunning victories to the Democratic Senate candidates over Republican incumbents.

The projected Democratic sweep means a 50-50 split in the Senate with Democrats holding the tie-breaking vote in Vice President Kamala Harris --giving Biden much freer rein to carry out priorities, starting with accelerating COVID relief.

Raphael Warnock, the pastor at the Atlanta church where Martin Luther King once preached, was projected to defeat Republican Kelly Loeffler.

Warnock, 51, would be just the third African-American to win a Senate seat from the South.

In the other Georgia race, Democrat Jon Ossoff, a 33-year-old video producer, was projected to defeat Republican David Perdue. —  AFP