Trump supporters storm US Capitol, clash with police; Biden says 'dark moment' in US history

In an unprecedented attack on democracy, thousands of angry supporters of President Donald Trump stormed the US Capitol and clashed with police, resulting in multiple injuries and interrupting a constitutional process to affirm Joe Biden's victory in the November presidential election.

The police, outnumbered by the protesters, had a tough time in managing the crowd on Wednesday, as hundreds of protesters breached security and entered the Capitol building, where members of the Congress were going through the process of counting and certifying the Electoral College votes. Both the House and Senate and the entire Capitol were placed under a lockdown.

Members of the US Congress were asked to get hold of the gas masks under their seats as the police resorted to tear gas to disperse protestors.

Multiple officers have been injured with at least one transported to the hospital, CNN reported, citing sources.

Trump, who earlier encouraged his supporters to head to the Capitol, urged them to abide by the law and go back home after the violent clash.

"I know you're hurt. We had an election that was stolen from us. It was a landslide election, and everyone knows it, especially the other side. But you have to go home. Now we have to have peace. We have to have law and order. We don't want anybody hurt,” Trump said in a short video posted on Twitter.

"There's never been a time like this, where such a thing happened, where they could take it away from all of us. From me, from you, from our country," he said.

"This was a fraudulent election, but we can't play into the hands of these people. We have to have peace. So go home," Trump said in the video message, which was flagged by Twitter to dispute the claim of election fraud. The micro blogging site added a stipulation that the tweet could not be replied to, retweeted or liked "due to a risk of violence." Earlier, Trump in a tweet asked his supporters to "remain peaceful." "Please support our Capitol Police and Law Enforcement. They are truly on the side of our Country. Stay peaceful!" Trump tweeted.

President-elect Biden said he was shocked and sad to see the US "come to such a dark moment".

"At this hour, our democracy's under unprecedented assault. Unlike anything we've seen in modern times. An assault on the citadel of liberty, the Capitol itself. An assault on the people's representatives and the Capitol Hill police, sworn to protect them. And the public servants who work at the heart of our Republic...," Biden said in an address to the nation.

"Let me be very clear. The scenes of chaos at the Capitol do not reflect a true America. Do not represent who we are. What we're seeing are a small number of extremists dedicated to lawlessness. This is not dissent. It's disorder. It's chaos. It borders on sedition. And it must end now," Biden said.

"I call on President Trump to go on national television now to fulfill his oath and defend the Constitution by demanding an end to this siege," he said.

White House Press Secretary Kayleigh McEnany said President Trump has directed the National Guard and other "federal protective services" to assist with responding to the rioters at the Capitol.

The state of Virginia is sending 200 state troopers and mobilising a unit of the Guard to quell the situation at the US Capitol, according to Clark Mercer, chief of staff for Governor Ralph Northam.

Multiple news outlets showed protestors walking with ease inside the Capitol and hundreds of them occupying the inaugural stage. A large number of them were seen climbing the wall.

Video taken at the US Capitol showed some rioters breaking the glass of a window and then climbing through the shattered pane.

"We're actually looking at video right now of these anarchists... these people who were involved in this insurrection. They broke the glass in the United States Capitol and now they are climbing through the window," CNN correspondent Dana Bash described the footage.

Vice President Mike Pence, who was inside the Capitol presiding over the joint session of the Congress, was evacuated from the building.

"The violence and destruction taking place at the US Capitol Must Stop and it Must Stop Now. Anyone involved must respect Law Enforcement officers and immediately leave the building," Pence tweeted.

"...this attack on our Capitol will not be tolerated and those involved will be prosecuted to the fullest extent of the law,” he said.

Washington DC Mayor imposed a city-wide curfew. This is possibly for the first time in the recent history that such a large number of people have breached into the US Capitol and disrupted the constitutional provisions. "There are no clear answers yet on when the joint session will resume to certify President-elect Joe Biden's win,” CNN reported, citing sources.

Congress had certified just 12 votes before the riots broke out. All 12 of those votes went to President Trump. There are 538 electoral votes in total.

Trump - who lost the popular and electoral college vote - continues to dispute the results.

Senator Ted Cruz said that the violence was unacceptable.

"Every American has the right to peacefully protest, but the violence we are witnessing on US Capitol grounds is unacceptable," Congressman Steve Womack said.

"US Capitol Police saved my life. Attacks on law enforcement officers trying to do their jobs are never acceptable. Period. We can passionately protest without being violent,” said House Republican Whip Steve Scalise.