A woman has died after being shot and an explosive device has reportedly been found as supporters of outgoing US President Donald Trump descended on the US Capitol.

Three other people died during the protests of "medical emergencies", Washington DC police confirmed, with officers making 52 arrests.

In dramatic scenes that drew international condemnation, supporters of the outgoing US president brought violence to the seat of America's democracy on Wednesday - prompting the US Capitol to be put into lockdown.

The White House revealed the US National Guard had been called in by Mr Trump following clashes between rioters and police, while a curfew has been ordered across the city.

As darkness fell, the FBI were also on the ground to clear remaining protesters.Advertisement

Groups of Trump supporters breached metal barricades and stormed their way into the Capitol building as they disrupted the confirmation of US president-elect Joe Biden's victory in November's election - a fortnight before his inauguration ceremony.

Local emergency services had earlier said one person was in a critical condition after being shot and at least five people - including a law enforcement officer - had been taken to hospital.

According to an NBC report, several officials said at least one improvised explosive device had been found on US Capitol grounds.

And Mr Trump's Republican Party - parts of whom the president has criticised for failing to fully support his unproven claims of election fraud - revealed a suspicious device was found at their headquarters before being detonated by a bomb squad.

Both chambers of Congress in Washington DC were abruptly recessed as they debated Mr Biden's election win - which Mr Trump continues to vociferously dispute - when the violence flared.

US Vice President Mike Pence was ushered out of the Senate chamber to a secure location as protesters entered the Capitol building.

In a televised address, Mr Biden said America's democracy was "under unprecedented assault" as he condemned the "small number of extremists dedicated to lawlessness" who had brought "chaos" to the US Capitol.

"This is not dissent, it's disorder. It's chaos. It borders on sedition and it must end, now," Mr Biden added.

"I call on this mob to pull back and allow the work of democracy to go forward."

The president-elect called on Mr Trump to go on national television to "defend the constitution" and "demand an end to this siege".

Mr Trump chose to post a minute-long video posted to his Twitter account.

He did not explicitly condemn the scenes of violence, but urged those who had gathered at the US Capitol to disperse.

"I know your pain, I know your hurt - we had an election that was stolen from us," he said.

"It was a landslide election and everyone knows it, especially the other side."

Calling on his supporters to leave the US Capitol, the president added: "You have to go home now, we have to have peace, we have to have law and order, we have to respect our great people in law and order.

"We don't want anybody hurt, it's a very tough period of time - there's never been a period of 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."

Twitter swiftly added a warning message to Mr Trump's video, which read: "This claim of election fraud is disputed, and this Tweet can't be replied to, Retweeted, or like due to a risk of violence."

Mr Trump and the Republicans have now also lost control of the US Senate as well as the White House, after the Democrats on Wednesday won two runoff senate races in the state of Georgia that had been too close to call in the November elections.

Mr Pence had earlier called for the "violence and destruction" to stop and warned "this attack on our Capitol will not be tolerated and those involved will be prosecuted to the fullest extent of the law".

The chaotic scenes came after Mr Pence had defied the president by saying he would not intervene in the confirmation of Mr Biden's victory by Congress.

Mr Trump turned on his vice-president, claiming Mr Pence "didn't have the courage to do what should have been done".

As the violence unfolded, Ivanka Trump - the president's daughter and adviser - deleted a tweet referring to "American Patriots" before she posted another tweet condemning "unacceptable" violence.

A 12-hour curfew, beginning from 6pm local time, was ordered in Washington DC by the city's mayor.

Former Republican president George W Bush said he and his wife, Laura, were "watching the scenes of mayhem... in disbelief and dismay".

"It is a sickening and heartbreaking sight," he said.

"This is how election results are disputed in a banana republic - not our democratic republic."

Prime Minister Boris Johnson condemned the "disgraceful scenes", adding: "The United States stands for democracy around the world and it is now vital that there should be a peaceful and orderly transfer of power."

Labour leader Sir Keir Starmer said: "Horrendous scenes from the US. These are not 'protesters' - this a direct attack on democracy and legislators carrying out the will of the American people."

NATO general secretary Jens Stoltenberg said: "The outcome of this democratic election must be respected."

Ursula von der Leyen, the president of the European Commission, posted on Twitter: "I believe in the strength of US institutions and democracy. Peaceful transition of power is at the core."

She added that Mr Biden "won the election" and said she would "look forward to working with him as the next President of the USA".

Mr Biden is due to be inaugurated as the next US president on 20 January, with a US Capitol ceremony set to take place where rioters gathered on Wednesday.