Donald Trump on Thursday acknowledged his presidency was ending and promised a smooth transition to Joe Biden in the wake of a mob attack by his supporters on the US Capitol now known to have left five people dead.

Supporters of US President Donald Trump gather for a rally in Washington
Supporters of US President Donald Trump gather for a rally in Washington AFP / Brendan Smialowski

After two of his cabinet secretaries quit in protest following Wednesday's mayhem, an unusually tame Trump condemned rioters who rampaged in his name through a congressional session that certified Biden's victory, although he did not go so far as to congratulate or even say the name of his successor.

"This moment calls for healing and reconciliation," Trump said in a video released on Twitter after a temporary suspension, a jarring shift of tone a day after a rally in which he encouraged thousands of supporters to march on the Capitol.

Democratic Senate candidate Raphael Warnock
Democratic Senate candidate Raphael Warnock AFP / JIM WATSON

"We have just been through an intense election and emotions are high, but now tempers must be cooled and calm restored," said Trump, standing before a lectern with the presidential seal.

"A new administration will be inaugurated on January 20. My focus now turns to ensuring a smooth, orderly and seamless transition of power," he said.

Democratic Senate candidate Jon Ossoff
Democratic Senate candidate Jon Ossoff AFP / JIM WATSON

"Serving as your president has been the honor of my lifetime," Trump said, without explicitly conceding and insisting he was "fighting to defend American democracy."

Trump's turnaround came as the two top Democrats in Congress urged his immediate removal, fearing damage he can still inflict in his less than two weeks left in the world's most powerful job.

IMAGES AND SOUNDBITES Hundreds of supporters of US President Donald Trump gather in Washington, DC, a day before a protest called by the outgoing US president who refuses to concede defeat in November 2020's election. The US Congress will meet Wednesday t
IMAGES AND SOUNDBITES Hundreds of supporters of US President Donald Trump gather in Washington, DC, a day before a protest called by the outgoing US president who refuses to concede defeat in November 2020's election. The US Congress will meet Wednesday to certify Democrat Joe Biden's electoral victory over Trump. AFPTV / Gilles CLARENNE

The editorial board of The Wall Street Journal piled on, calling for Trump "to take personal responsibility and resign."

"It is best for everyone, himself included, if he goes away quietly," said the newspaper, which is owned by conservative media tycoon Rupert Murdoch.

Outgoing president Donald Trump was due to address his supporters in Washington as Joe Biden's victory is certified
Outgoing president Donald Trump was due to address his supporters in Washington as Joe Biden's victory is certified AFP / Brendan Smialowski

Biden, who won seven million votes more than Trump in the November 3 election as well as a decisive edge in the vital state-by-state Electoral College, declined to address demands for Trump's removal but accused him of an "all-out assault on the institutions of our democracy."

"Yesterday, in my view, was one of the darkest days in the history of our nation," Biden said at an event to introduce his nominee for attorney general, respected judge Merrick Garland, who if confirmed will quickly need to decide whether to prosecute Trump.

Crowds of people gather as US President Donald Trump speaks to supporters before Congress meets to certify Joe Biden's election win
Crowds of people gather as US President Donald Trump speaks to supporters before Congress meets to certify Joe Biden's election win AFP / MANDEL NGAN

"They weren't protesters," Biden said. "They were a riotous mob, insurrectionists, domestic terrorists."

"I wish we could say we couldn't see it coming but that isn't true. We could see it coming."

Top Senate Democrat Chuck Schumer stands with Senate Republican leader Mitch McConnell in a session to certify Joe Biden's election victory
Top Senate Democrat Chuck Schumer stands with Senate Republican leader Mitch McConnell in a session to certify Joe Biden's election victory POOL / KEVIN DIETSCH
Police hold back supporters of US President Donald Trump as they gather outside the US Capitol's Rotunda
Police hold back supporters of US President Donald Trump as they gather outside the US Capitol's Rotunda AFP / Olivier DOULIERY

House Speaker Nancy Pelosi and Senate Democratic leader Chuck Schumer urged Vice President Mike Pence to invoke the 25th Amendment, which allows a majority of the cabinet to remove a president deemed unable to discharge his duties.

Democratic Senate candidate -- and projected winner -- Jon Ossoff
Democratic Senate candidate -- and projected winner -- Jon Ossoff AFP / JIM WATSON

They threatened to impeach Trump for an unprecedented second time in the hopes that the Senate will oust him.

"This is an emergency of the highest magnitude," Pelosi said, describing Trump as a "very dangerous person."

Democratic Senate candidate Raphael Warnock
Democratic Senate candidate Raphael Warnock AFP / JIM WATSON

"By inciting sedition, as he did yesterday, he must be removed from office," she said. "While it's only 13 days left, any day can be a horror show for America."

Few Republicans came forward to back such remedies, although Representative Adam Kinzinger, a frequent Trump critic within his party, said it was time to "end this nightmare" and also called for invoking the 25th Amendment, which would make Pence the acting president.

IMAGES AND SOUNDBITES Hundreds of supporters of US President Donald Trump gather in Washington, DC, a day before a protest called by the outgoing US president who refuses to concede defeat in November 2020's election. The US Congress will meet Wednesday t
IMAGES AND SOUNDBITES Hundreds of supporters of US President Donald Trump gather in Washington, DC, a day before a protest called by the outgoing US president who refuses to concede defeat in November 2020's election. The US Congress will meet Wednesday to certify Democrat Joe Biden's electoral victory over Trump. AFPTV / Gilles CLARENNE

"The president is unfit," Kinzinger said. "And the president is unwell."

Speaking to CNN, retired Marine Corps general John Kelly, who served as Trump's chief of staff for 18 months, said the cabinet should consider the 25th Amendment but believed the president had been chastened.

"He can give all the orders he wants but no one is going to break the law," Kelly said.

Pence, loyally by Trump's side until the final days, rejected Trump's vocal pressure to somehow intervene in Wednesday's session, which has taken place every four years for over two centuries without drama.

In the middle of the night, after hours of delay due to the riots and Trump loyalists' contesting of the results, it was Pence who formally announced the victory of Biden as the 46th president and Kamala Harris as the next vice president.

Transportation Secretary Elaine Chao, who is married to Republican Senate leader Mitch McConnell and is one of Trump's longest-serving cabinet members, announced she would resign over the "entirely avoidable" violence at the Capitol.

On Thursday evening Education Secretary Betsy DeVos became the second cabinet member to quit, telling Trump in a letter that such "behavior was unconscionable for our country."

Others who resigned included Mick Mulvaney, a former Trump chief of staff who is now US special envoy to Northern Ireland, and the deputy national advisor, Matt Pottinger, an architect of Trump's hawkish line on China.

The torrent of condemnation came as Capitol Police said Officer Brian Sicknick had died at a hospital of injuries sustained during clashes with the crowd-waving mob, which overwhelmed police and forced their way into the legislature.

It was the first law enforcement death from a day of violence which also left four protesters dead, including a woman who was shot and killed by police.

Three other deaths were reported on the Capitol grounds, but the circumstances remained unclear.

Bipartisan anger has mounted since the riot over the failure of law enforcement to prevent the mobs from entering Congress.

Steven Sund, the chief of the 2,300-strong Capitol Police, handed in his resignation, and lawmakers vowed a thorough investigation on security lapses.

Many questioned how police would have responded had the crowd been not overwhelmingly white Trump supporters but Black anti-racism protesters, who were met with force in nationwide demonstrations last year.

The controversy spread beyond Washington.

"I think the most worrying thing about the recent events is the degree of police complicity with the right-wing extremists," said Daniel Colligan, a sociology professor who was among hundreds in New York marching Thursday night to Schumer's home to demand Trump's immediate ouster.

"True progress will be possible only once we acknowledge that this disconnect exists and take steps to repair it," she said.

"And that also means coming to grips with the reality that millions voted for a man so obviously willing to burn our democracy to the ground for his own ego."