In addition to Boris Johnson, other world leaders are weighing in on the latest disruptions to the US electoral process.

Canadian Foreign Minister François-Philippe Champagne tweeted: "Canada is deeply shocked by the situation in Washington DC. The peaceful transition of power is fundamental to democracy - it must continue and it will. We are following developments closely and our thoughts are with the American people."

In a statement, the French foreign ministry condemned the protests as a "serious attack on democracy".

Dutch Prime Minister Mark Rutte tweeted: "Horrible images from Washington DC. Dear @realDonaldTrump, recognise @JoeBiden as the next president today."

President of the European Council Charles Michel tweeted: "The US Congress is a temple of democracy. To witness tonight’' scenes in #WashingtonDC is a shock. We trust the US to ensure a peaceful transfer of power to @JoeBiden".

The EU's foreign policy chief, Josep Borrell, added: "This is an unseen assault on US democracy, its institutions and the rule of law. This is not America. The election results of 3 November must be fully respected."

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Amid the bedlam at Capitol Hill, many are comparing the response by law enforcement to pro-Trump protesters today with that of Black Lives Matter (BLM) protesters across the country this summer.

"Imagine if #BlackLivesMatter were the ones who were storming the Capitol building," wrote CNN political commentator Van Jones. "Thousands of black people laying siege to the seat of government."

BLM protests this summer were frequently met with police and National Guard members decked out in riot gear. The mostly peaceful demonstrations resulted in dozens of arrests and some 20 deaths of protesters, according to the Armed Conflict Location and Event Data project.

Demonstrators in Washington DC today were able to breach the temporary barriers set up outside the Capitol building.

Footage appears to show police officers - who were vastly outnumbered - opening the gates to allow protesters through, while members of law enforcement posed for selfies with the demonstrators who had broken inside the building.

One person has been shot during violent protests inside the US Capitol, according to the Associated Press.

Lindsay Watts, a reporter with a Fox News affiliate, tweeted that DC paramedics said resuscitation efforts were under way.

News that a woman was in a critical condition after being shot in the chest was also reported by CNN.

UK Prime Minister Boris Johnson took to Twitter a short while ago to decry the scenes from Washington DC and reiterate calls for a peaceful transfer of power in the US.

If you're just joining our live coverage, here's how the day unfolded:

• It began with good news for Democrats as they looked poised to take control of the US Senate with two projected wins in Georgia
• President Donald Trump addressed supporters in Washington DC, saying he would "never concede" and that now was not the time for "weakness"
• As Trump wrapped up his speech, Congress convened a joint session to certify the results of the 2020 election - and Joe Biden's win. It is the final step before Biden's inauguration as the 46th president on 20 January
• Seeking to disrupt the proceedings in Congress, a large group of pro-Trump supporters breached barricades, scaled walls and forced lawmakers to evacuate the premises. The violence has continued for hours.
• The DC National Guard has been deployed to the Capitol, to back up law enforcement at the scene.

Image source, Reuters

President-elect Joe Biden has called on President Donald Trump to "fulfil his oath and defend the Constitution - and demand an end to this siege".

"The attack on the Capitol is not a protest, it's an insurrection," he said.

The escalating unrest put an abrupt halt to a joint session of Congress scheduled to certify Biden's election win as the next president.

"Democracy is fragile," said Biden. "To preserve it requires leaders who are devoted not in personal power, but in the common good."

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This is probably a good time to go over the facts of the election results, contrary to what President Trump has just repeated on video.

• Democrat Joe Biden won 306 votes to Trump's 232 in the US electoral college, which confirms the US president. Biden far exceeded the 270 needed to win the presidency
• In the popular vote, Biden secured at least seven million more ballots than Trump
• The Trump campaign has filed nearly three dozen lawsuits challenging the election results. They have all proved fruitless.
• Trump appointee Attorney General William Barr, who resigned in December, said last month that his justice department had found no proof to back Trump's comments relating to election fraud

Donald Trump has shared a new video, just minutes after President-elect Joe Biden called on him to address the nation and put a halt to the pro-Trump protests occurring in Washington DC and around the country.

"I know your pain. I know your hurt," says Trump, again falsely claiming that the election was "stolen".

"Everyone knows it. Especially the other side. But you have to go home now."

Borrowing one of his own campaign slogans, he adds: "We have to have peace. We have to have law and order.

"This was a fraudulent election but we can't play into the hands of these people. We have to have peace."

Trump's election fraud claims fact-checked

Laura Trevelyan
BBC World News America presenter, Capitol Hill

On the steps of Capitol Hill, hundreds of loyal Trump supporters are packed closely together, as nearby armed police officers keep a watchful eye.

The mood here is tense and defiant.

"We're not [expletive] Antifa!" one man screams at the police, referring to the loose coalition of "anti-fascist" activists that oppose Trump.

Trump loyalists near him wave placards that say "show us the ballots".

"All we want is for the Capitol police to stand down, and surrender the building to us," says one man to news cameras, as he is filmed by other Trump supporters.

The conviction here is that the election was stolen from President Trump, and the lawmakers inside the building should do their duty and somehow award the election to him.

Never mind that election officials have certified the results and the courts have thrown out Trump campaign lawsuits alleging fraud because there's no evidence.

It's a siege mentality here, as word spreads through the crowd that the National Guard are on their way to the US Capitol building.

A pro-Trump protester is pictured making himself at home in the office of House Speaker Nancy Pelosi.

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Elsewhere, police in Washington DC use tear gas in an attempt to disarm demonstrators, who so far appear to be ignoring calls for peace from US officials.

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President-elect Joe Biden is addressing the nation from Wilmington, Delaware, calling on the pro-Trump "mob" to "pull back and allow the work of democracy to move forward".

"It's not a protest, it's an insurrection," Biden says, asking Donald Trump to "step up", go on television and "demand an end to this siege".

"Enough is enough," he says.

Pictures from the scene show protesters, a few of them armed, marching through the halls of Congress.

Reports say that a fire extinguisher was set off and a woman was shot inside the building. The seriousness of her injuries is not known.

Image source, Getty Images

Nearly all of those protesting in Washington are holding signs or flags bearing Trump's name, or wearing pro-Trump merchandise.

Some have been seen wearing outfits that promote the QAnon conspiracy theory, which claims that Trump is working to bust a secret ring of paedophile elites.

A few Confederate flags have been spotted as well. To remind you, the Confederacy is the rebellion that sought to secede from the United States in the 1860s, and fought to preserve the legal right to own slaves.

Some protesters are wearing body armour and tactical gear, and have been seen engaging in violent clashes with police.

What is QAnon?

Image source, Getty Images

The National Guard has been called, at President Trump's request, says the White House press secretary Kayleigh McEnany.

The president previously tweeted at his supporters to remain peaceful after riling up the same crowd in a rally this morning.

The vice-president has asked Trump supporters to leave the Capitol and stop the violence.

"This attack on our Capitol will not be tolerated and those involved will be prosecuted to the fullest extent of the law," Mike Pence tweeted.

Pence, who has insisted he cannot overturn the results of the election despite pressure for the president, was presiding over the electoral college vote when protesters stormed the building and he was shepherded to safety.

Capitol police have detained some protesters as they continue to storm the building.

Some demonstrators have broken into the Senate chamber, climbing on the side of the walls as police drew their weapons.

Image source, Getty Images

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Trump has just tweeted another message to protesters who have stormed the US Capitol, saying: "No violence!"

Laura Trevelyan
BBC World News America presenter, Capitol Hill

Sirens are wailing outside Capitol Hill, and police are swarming everywhere - camouflaged tactical officers are the latest to arrive.

Trump protesters are on the steps of the Capitol Hill rotunda, and some are on the balcony, waving flags and shouting "USA" and chanting "stop the steal".

It’s a tense and volatile atmosphere, and not what a peaceful transfer of power looks like.

Capitol Hill police are calling for reinforcements as the violence continues at the Capitol.

A spokesperson for the Department of Homeland Security said members of the US Secret Service and the Federal Protective Service are currently meeting calls to provide assistance.

The Department of Defense has not yet decided to deploy the National Guard to back up law enforcement on the scene.

Protesters who have stormed the US Capitol are trespassing on federal property and may face charges.

Protesters have continued to swarm the Capitol, some posing for photos in the Capitol rotunda.

Chants of "We Want Trump" echo through the hallways as press and lawmakers are taken to an undisclosed location for safety.

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After a summer of protests against coronavirus lockdown measures, including in Michigan where armed militia members stormed the state capitol, we're now seeing similar scenes playing out in Washington DC.

While both chambers of the US Congress were meeting on Wednesday to certify Democrat Joe Biden's win over Donald Trump, the proceedings were interrupted by police clashes with armed pro-Trump protesters in adjoining corridors.

Trump has for weeks claimed to have been the true winner, saying without evidence that the votes cast for Biden in crucial swing states were fraudulent.

He and his supporters have been pressing Vice-President Mike Pence to overturn the election result by refusing to certify Biden's win, something that experts agree he does not have the legal power to do.

In the days leading up to the certification, Trump said that he would attend the "Save America" rally happening in Washington on Wednesday, promising on Twitter that it would be "very big" and "wild".

About an hour after Trump addressed thousands on the National Mall, promising to "never concede" that he had lost, chaos was unleashed.