Thousands of US President Donald Trump’s supporters have returned to Washington for rallies to back his desperate efforts to overturn his election defeat.

They cheered as Mr Trump flew overhead in the Marine One helicopter on his way out of town for a US Army-Navy American football game in New York on Saturday.

Supporters cheered as Donald Trump flew overhead. Photo: Getty

Later, Mr Trump threw fuel on the fire of their anger with a series of incendiary tweets.

“This is a great and disgraceful miscarriage of justice. The people of the United States were cheated, and our Country disgraced. Never even given our day in Court!” Trump wrote on Twitter on Saturday morning.

“The Supreme Court had ZERO interest in the merits of the greatest voter fraud ever perpetrated on the United States of America.”

As night fell on the US capital the anger of Trump supporters spilled into violent clashes between ultra-right Proud Boys activists, groups defending the integrity of the election and police.

DC: Proud boys and Antifa/BLM brawl #tatumreport #drewhernandez pic.twitter.com/kIBKph8b3S

— Drew Hernandez (@DrewHLive) December 13, 2020

The rallies are intended as a show of force just two days before the Electoral College meets to formally elect Joe Biden as the 46th president.

Mr Trump, whose term will end on January 20, refuses to concede, while clinging to baseless claims of fraud that have been rejected by state and federal courts, and on Friday by the Supreme Court.

The president tweeted his apparent surprise on Saturday morning (local time) at the rallies, publicly known for weeks.

“Wow! Thousands of people forming in Washington for Stop the Steal. Didn’t know about this, but I’ll be seeing them! (hash)MAGA.”

Wow! Thousands of people forming in Washington (D.C.) for Stop the Steal. Didn’t know about this, but I’ll be seeing them! #MAGA

— Donald J. Trump (@realDonaldTrump) December 12, 2020

Mr Trump left the White House around noon for the trip to the US Military Academy, and as Marine One passed over the the rally on the National Mall, cheers went up.

Michael Flynn, the former national security adviser recently pardoned by Trump, was speaking from the stage at the time.

“That’s pretty cool. Imagine just being able to jump in a helicopter and just go for a joy ride around Washington,” said Mr Flynn, whose pardon wiped away his conviction for lying to the FBI during the Russia investigation.

At a pro-Trump demonstration in Washington a month ago, Mr Trump thrilled supporters when he passed by in his motorcade en route to his Virginia golf club.

Photo: Getty

Saturday’s gathering on the National Mall, called the “Jericho March”, was described on its website as a “prayer rally” with speakers “praying for the walls of corruption and election fraud to fall down”.

A separate rally was taking place on Freedom Plaza downtown.

The organisers seemed intent on avoiding confrontations, telling demonstrators to avoid certain hotels and marking off large chunks of downtown Washington as a “no-go zone”.