SUPPORTERS of the defeated US president Donald Trump last night stormed buildings in Washington DC causing the Capitol building to be locked down with lawmakers inside.

The mob made their way in as lawmakers held a session to certify Joe Biden's election win. They marched through corridors, breaking windows and doors to enter, with many chanting "stop the steal".

It has emerged that one of the protesters was shot dead by police while three others died of "medical emergencies".

Some 52 people have been arrested, most of them for curfew violations. 

CNN reported an "armed stand-off" outside the House floor as law enforcement officers request back up. Tear gas was also used inside the rotunda, the symbolic and physical heart of the US Capitol building. 

The National: Security services face down an armed protester outside the door of the HouseSecurity services face down an armed protester outside the door of the House

Police sent an alert to those inside the building which read: "Internal Security Threat: move inside office/lock doors, seek cover, and remain silent."

A pipe bomb was also reported causing other buildings to be evacuated, according to one US politician. 

In response to the violence, Trump tweeted: "Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution, giving States a chance to certify a corrected set of facts, not the fraudulent or inaccurate ones which they were asked to previously certify. USA demands the truth!"

He tweeted again: "Please support our Capitol Police and Law Enforcement. They are truly on the side of our Country. Stay peaceful!"

Trump wrote: "I am asking for everyone at the U.S. 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. Thank you!"

After hours of chaos Trump posted a video clip asking his supporters to go home, but repeating the false claim that the election was rigged. To those supporters in the Capitol he added: "We love you."

Twitter and Facebook have locked the president's accounts after the incident. 

For most of last night's events Trump sat in the Oval Office about two miles from the epicentre of the violence.

Earlier yesterday, Trump encouraged his supporters to go to the Capitol building and "Save America".

Protesters stormed the building and held the House floor, with one reportedly standing on the dias and shouting "Trump won this election".

US Congress was officially counting the electoral college votes of the election, which Trump lost to Joe Biden, inside the Capitol building in Washington DC. Biden beat Trump by 306 electoral college votes to 232, the same margin which Trump called a "landslide" when he beat Hillary Clinton in 2016.

Supporters of the outgoing president, convinced the result is fraudulent and was stolen by the Democrats despite overwhelming evidence to the contrary, became violent.

One Elijah Schaffer, who appears to support Trump, shared a video of protesters storming the Capitol, saying it was the "craziest thing I’ve ever seen in my life".

In another tweet, the host of the "Slightly Offensive" podcast wrote: "Patriots have stormed the Capitol building ground and are breaching federal barriers and police in the masses.

"Non lethal force in effect. Full unlawful assembly in display. Never seen anything like this. Insane. Thousands occupying."

HuffPost's Philip Lewis also shared video of the ongoing situation in which those trying to get past the police can be seen to be pepper-sprayed.

Lewis wrote: "Whoa: Trump supporters going at it with the police on the steps of the Capitol as Congress counts the Electoral College ballots inside."

Elaine Luria, a navy veteran who serves as the Representative for Virginia's 2nd congressional district, said she "just had to evacuate my office because of a pipe bomb reported outside".

She went on: "Supporters of the President are trying to force their way into the Capitol and I can hear what sounds like multiple gunshots."

Ted Lieu, the Representative for California's 33rd congressional district, tweeted: "Dear Donald Trump enablers: You will not intimidate us.

"Today both the Senate and House will vote multiple times to reject your delusional conspiracy theories and affirm the certified Electoral College results. Your toxic beliefs will be thrown into the ash heap of history."

Yesterday Trump told thousands of his supporters gathered in Washington DC that "we will never concede" the presidential election.

Trump addressed a "Save America" rally on the Ellipse, just south of the White House, following speeches by his sons Eric and Donald Jr.

He urged Vice President Mike Pence to help overturn Joe Biden's victory in the November election when Congress sits to certify the Electoral College votes.

"If Mike Pence does the right thing we win the election," Trump said.

"All Vice President Pence has to do is send it back to the states to recertify and we become president and you are the happiest people," Trump said, repeating a falsehood he has been promoting leading up to the congressional session.

But Pence later defied the president's call, saying "he does not have the power to discard electoral votes".

The vice-president issued a statement saying it was "my considered judgment that my oath to support and defend the Constitution constrains me from claiming unilateral authority to determine which electoral votes should be counted and which should not".

Earlier yesterday Trump tweeted to his 88 million followers: "Get smart Republicans. FIGHT!"