Hundreds of supporters of President Donald Trump have stormed the US Capitol in a bid to overturn his election defeat, occupying the symbol of American democracy and forcing Congress to temporarily postpone a session to certify President-elect Joe Biden’s victory.

Police on Wednesday (local time) evacuated lawmakers and struggled for more than three hours to clear the Capitol of Trump supporters, who surged through the halls and rummaged through offices in shocking scenes of chaos and mayhem.

Four people died in events surrounding the incursion.

Washington, DC, Police Chief Robert Contee said the dead included a woman who was shot by US Capitol Police, as well as three others who died in “medical emergencies.”

The FBI said it had disarmed two suspected explosive devices.

Police declared the Capitol building secure shortly after 5.30pm and lawmakers reconvened shortly after 8pm to resume the election certification.

“To those who wreaked havoc in our Capitol today – you did not win,” Vice-President Mike Pence said as the session resumed. “Let’s get back to work,” he said, drawing applause.

US Vice-President Mike Pence makes remarks as the US Senate reconvenes to resume debate on the electoral vote count. Photo: Slipa USA

“We will certify the winner of the 2020 election,” Senate Republican leader Mitch McConnell added, calling the assault by Trump supporters a “failed insurrection”.

Former US president Barack Obama says the storming of the US Capitol was incited by Mr Trump.

“History will rightly remember today’s violence at the Capitol, incited by a sitting president who has continued to baselessly lie about the outcome of a lawful election, as a moment of great dishonour and shame for our nation,” Mr Obama said in a statement on Wednesday.

In a similar vein, Senate Democratic leader Chuck Schumer said Mr Trump “bears a great deal of the blame” for the day’s events.

As the Senate reconvened to count electoral votes that will confirm Democrat Joe Biden’s win, Mr Schumer said that January 6, 2021, will “live forever in infamy” and will be a stain on the democracy.

Mr Schumer said the events “did not happen spontaneously”.

He said Wednesday: “The President, who promoted conspiracy theories that motivated these thugs, the President, who exhorted them to come to our nation’s capital, egged them on.”

Mr Schumer said the protesters should be prosecuted to the fullest extent of the law.

Mr Trump has falsely claimed that there was widespread fraud in the election to explain away his defeat.

As the President continued to make the unsubstantiated claims, Twitter  locked his account while Facebook and YouTube took down his video message to protesters who stormed the US Capitol.

Lawmakers were debating a last-ditch effort by pro-Trump lawmakers to challenge the results, which was unlikely to succeed. But some who had planned to object said they would cut their effort short and perhaps only challenge the results in one state instead of multiple states.

Washington Mayor Muriel Bowser ordered a citywide curfew starting at 6pm. National Guard troops, FBI agents and US Secret Service were deployed to help overwhelmed Capitol police, and Guard troops and police pushed protesters away from the Capitol after the curfew took effect.

“This is how election results are disputed in a banana republic — not our democratic republic. I am appalled by the reckless behaviour of some political leaders since the election,” former President George W. Bush, a Republican, said in a statement, without mentioning Mr Trump by name.

Trump supporters broke windows and police deployed tear gas inside the building. Washington Metropolitan Police Chief Robert Contee said members of the crowd used chemical irritants to attack police and several had been injured.

It was the most damaging attack on the iconic building since the British army burned it in 1814, according to the US Capitol Historical Society.

The chaotic scenes unfolded after Mr Trump, who before the election refused to commit to a peaceful transfer of power if he lost, addressed thousands of supporters near the White House, repeating unfounded claims that the election was stolen from him due to widespread fraud and irregularities.

Mr Trump told the supporters they should march on the Capitol to express their anger at the voting process and pressure their elected officials to reject the results, urging them “to fight”.

Mr Biden, a Democrat who defeated the Republican president in the November 3 election and is due to take office on January 20, said the activity of the protesters “borders on sedition”.

-with agencies