Our senior reporters in the US have given some instant analysis of the incredible scenes unfolding in Washington right now.

Lawmakers and reporters inside the building say they have been asked to evacuate, shelter in place and put on gas masks.

Both chambers of US Congress abruptly stopped proceedings as they were debating November's election results.

Here's what happened in the Senate.

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As his supporters storm into the US Capitol in quickly-escalating protests, Donald Trump has broken his silence and tweeted for demonstrators to "support Capitol Police and Law Enforcement".

"They are truly on the side of our country," he wrote. "Stay peaceful!"

US media report that tear gas has now been used inside the Capitol building as a growing number of demonstrators enter the building.

DC Mayor Muriel Bowser has ordered a citywide curfew beginning at 1800 EST.

Chaos has broken out within the US Capitol as pro-Trump supporters break into the building.

The ongoing special House and Senate sessions have been recessed amid the escalating clashes between protesters and police.

Lawmakers had gathered to confirm the election of Democratic President-elect Joe Biden - an outcome rejected by protesters.

Photos show demonstrators gathered just outside the Senate chamber. Other images show demonstrators carrying firearms.

Capitol Police have put the US Capitol Building on lockdown amid violent clashes between police and Trump supporters, gathered to protest the 2020 election results.

Footage shows demonstrators swarming the Capitol building, breaking the temporary barrier that had been put in place ahead of today's events. US media describe some protesters climbing on parts of the Capitol building, attempting to get inside.

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As Republicans in Congress push forward with an attempt to block the certification of election results, Republican Senate leader Mitch McConnell condemned his colleagues and warned they could "damage our Republic forever".

Speaking directly to his party members on the Senate floor, McConnell urged them to reconsider their actions: "If this election were overturned by mere allegations from the losing side, our democracy would enter a death spiral."

"The voters, the courts and the states have all spoken," he said, pointing out none of the allegations posed by lawmakers could change the result - Joe Biden's victory.

"We cannot simply declare ourselves a national board of elections on steroids."

The challenge to the election results is not likely to succeed, but it will prolong matters in the chamber.

The BBC's Hadi Nili is in Atlanta, Georgia, where armed protesters are marching to the state's capitol building in protest against the election results there, and in support of Donald Trump.

In Washington DC, where Trump is speaking, protesters are banned from carrying firearms. Despite the city's laws, several people at Trump's "Save America" rally have already been arrested on gun charges.

But in Georgia, supporters are permitted to openly carry weapons, as Hadi's video here shows.

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Quite a lot.

Inside the US Capitol, lawmakers have convened for a special session to affirm the 2020 election results - counting and confirming electoral college votes.

The electoral college, the system used to select the US president, has already certified Biden's victory.

Today's proceedings to formally select the president are usually brief and ceremonial. But it is unusually controversial this year, with some Republicans loyal to Trump promising to overturn the result by formally objecting at the session.

Already, Republican Senator Ted Cruz and Representative Paul Gosar have contested electoral votes cast by Arizona for Joe Biden. Several more objections are expected to follow.

Still, this bid is almost certain to fail and Biden will be one step closer to assuming the presidency and being sworn in on 20 January.

Read more about how this process works

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If you're just joining our live coverage, here's a quick recap of the main stories so far today:

• Democrat Rev Raphael Warnock, pastor of the Baptist church often considered the spiritual home of the US civil rights movement, is projected to make history as the first black senator for the state of Georgia
• The other Senate run-off election in Georgia last night does not yet have a projected winner, but Democrat Jon Ossoff is inching toward a victory that will return control of the Senate to the Democrats
• President Donald Trump has spoken to supporters in Washington DC, telling them he "will never concede" in presidential election
• Trump's refusal to concede is unlikely to matter much after today, as Congress is meeting now to certify the results of the 2020 election - and Joe Biden's win. It is the final step before Biden's inauguration as president on 20 January.

Barbara Plett Usher
BBC News, Washington

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For many of the people here, this is about more than President Trump. It's an existential crisis for the United States.

They tell me they need to protect the constitution and stand up for American freedoms. They believe that the Democrats have "stolen" the election and that the country's institutions have been complicit.

When I point out there's no evidence of fraud, they say yes there is, but the courts are not listening and the mainstream media isn't reporting on it. They're afraid the Democrats will bring socialism, are in cahoots with China, will crush their individual freedoms, and so on.

Some have told me they're afraid of civil war. Some have said they're ready to fight, and one has indicated vaguely that he and his group are planning resistance.

Admittedly, these are the most dedicated Trump supporters and some believe fringe conspiracy theories. But polls show a majority of Republicans don't accept Joe Biden's win as legitimate.

So political tension will continue, and possibly political violence.

Image source, EPA

In his lengthy written statement, Vice-President Mike Pence says that his "largely ceremonial" role in today's special Congressional session does not allow him to reverse the 2020 election results and Joe Biden's win.

The statement comes as President Donald Trump continues to exert public pressure on his vice-president, telling supporters at his rally in Washington DC that he would be "very disappointed" in Pence if he did not heed the call to reject the election results.

Pence has faced intense pressure from Trump and a growing number of Republican lawmakers to push back on Biden's win.

But in his statement, Pence wrote that it was his "considered judgment" that the US Constitution prevents him from doing so.

"The Presidency belongs to the American people, and to them alone," Pence wrote.

And he's right. The vice-president has no legal authority to declare Biden's election victory invalid.

Read more about what Mike Pence can - and can't - do in Congress today.

A rare joint session of Congress is now under way in the House of Representative, to certify Joe Biden's election win.

It's presided over by Vice-President Mike Pence.

Here's what to expect from Congress

Vice-President Mike Pence has issued a statement saying he cannot overturn or reject Joe Biden's election win, despite ongoing pressure from Donald Trump.

More coming on this shortly.

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Senate Minority Leader Chuck Schumer has congratulated Democrats Raphael Warnock and Jon Ossoff on their Senate runs, celebrating a "brand new day" for their party.

Warnock's projected win, and Ossoff's narrow lead, puts the Democrats within striking distance of a Senate majority for the first time in six years. It also means Schumer is poised to take control of the chamber as majority leader.

Schumer praised Warnock and Ossoff as "outstanding" future senators, and noted the historic nature of Warnock's win.

"When Raphael Warnock was born, both of Georgia's senators were segregationists. Yesterday, Georgia just elected its first African American to the United States Senate in its history."

A Democratic majority in the Senate will give Schumer and his party a much better chance at pushing through their legislative agenda.

"Four more years - I thought it would be easy," says Trump as he lists his accomplishments in office including the creation of the Space Force branch of the military.

"We've done things that nobody ever even thought possible and that's part of the reason that many people don't like us - because we've done too much."

Read more below on how we've tracked his presidential pledges.

Did Trump keep his promises?

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President-elect Joe Biden has tapped Judge Merrick Garland as his nominee for attorney general, CBS News reports.

Garland, 68, is the chief judge of the second most important court in the US.

He previously worked in the Department of Justice under the Bill Clinton administration, where he oversaw several high-profile prosecutions.

In 2016, then-President Barack Obama nominated Garland to the US Supreme Court to fill the vacant seat created by the death of Justice Antonin Scalia, but Republican senators refused to consider him.

Biden's selection of Garland comes on a day that Democrats look poised to take back control of the Senate, where cabinet nominations are approved.

Attorney General is the top law enforcement job in the US, mainly filled by Bill Barr under Trump.

The president is right about one thing, however. There are thousands of people braving wintry weather to show their support.

Here's a view of Washington DC's National Mall, where his supporters are gathered to watch him speak.

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