US President Donald Trump has made his first public admission that Democratic rival Joe Biden won the recent US election - before quickly reversing course to claim he won, and again push unsubstantiated claims of mass electoral fraud.

He claimed on Twitter: "He won because the election was rigged." 

There is no evidence that this is the case and Twitter flagged the tweet with a warning: "This claim about election fraud is disputed."

Mr Trump later tweeted: "He only won in the eyes of the fake news media. I concede NOTHING! We have a long way to go. This was a rigged election!" Twitter again put a warning on the tweet.

Tens of thousands of people marched in Washington DC yesterday to show their support for the Republican leader. 

The rally was largely peaceful but there were some clashes between pro-Trump supporters and counter-protesters.

One stabbing was reported, two police officers were injured and several firearms were seized. Police arrested at least 20 people.

Earlier, President Trump tweeted pictures of the large crowds who said they would not stand for "corruption". 

Despite losing the election to Democratic opponent Joe Biden, President Trump has refused to concede and has repeatedly claimed - without evidence - that there has been election fraud.

Mr Trump embarked on a drive-by in his armoured motorcade, on his way to and from Virginia to play golf, smiling through his limousine window to wild cheers and signs saying "Best prez ever" and "Trump 2020: Keep America Great."

Donald Trump waving to supporters from his armoured car as he left his golf club in Virginia yesterday

"We wanted to show our support, we're feeling they are trying to steal the election," said Pam Ross, who drove eight hours from Ohio to join the rally, referring to the president's political opponents.

Thousands of pro-Trump supporters marched in Washington DC

"President Trump deserves to see who's behind him, he deserves to feel the love," Kris Napolitana, from Baltimore, told AFP. "I believe that he's going to win when all the fraud and cheating is found out."

With right-wing militia group the Proud Boys among those attending, a large security presence was deployed to prevent clashes with anti-Trump events outside the Supreme Court.

As night fell, police formed lines on either side of a street leading to the White House, separating hundreds of rival protesters.

"We're just holding back people who want to fight," one officer told AFP.

After dark, groups of Trump supporters and counter-protesters clashed on the streets, scuffling and throwing punches, video posted by the Washington Post showed.

Groups of Antifa protesters and Proud Boys clashed as darkness fell in Washington DC

President Trump seemed to be following the evening's events, taking to Twitter to accuse the city's mayor of "not doing her job" and calling on the police to "get going - do your job and don't hold back".

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The latest vote tallies gave the Democrat Joe Biden a clear win in the state-by-state Electoral College that decides the presidency, with 306 votes against Trump's 232.

But Margarita Urtubey, 49, a horse breeder from Miami, said the election was "so corrupt," adding: "Trump won by a landslide. We are here to march for the 'stop the steal' of this election, to make our voice heard."

Mr Trump tweeted that "hundreds of thousands" had turned out - while his spokeswoman Kayleigh McEnany made the greatly exaggerated claim that more than a million people were present.

But the turnout was undoubtedly high for a strongly Democratic city, boosted by protesters from around the US.

Kathlin Erickson, who said she flew from Colorado on a plane "filled with Trump supporters," was asked about a possible second Trump administration.

"A Trump victory? That's a long shot, but anything is possible with God," she said.

President Trump is impeding Biden's transition ahead of the inauguration on 20 January, 2021 and has filed numerous lawsuits - unsuccessfully - to challenge vote counts around the country.

The Republican leader said on Friday "time will tell" if he remains president, in a momentary slip of his refusal to concede defeat.

Meanwhile president-elect Joe Biden went biking in a Delaware state park with his wife Jill yesterday and a security detail. When asked if he was closer to choosing his cabinet, he replied "yes".

US President Elect Joe Biden and wife Jill on a bike ride in Cape Henlopen State Park, Delaware

Additional reporting: AFP