(Adds details on tensions between protest groups in Washington)
By Jonathan Landay and Timothy Gardner
WASHINGTON, Dec 12 (Reuters) - Conservative groups alleging without evidence that President-elect Joe Biden stole the U.S. election gathered for protests across the country on Saturday, including one in Washington that threatened to turn violent as darkness fell.
Organizers of Stop The Steal, linked to pro-Trump operative Roger Stone, and church groups urged supporters to participate in "Jericho Marches" and prayer rallies.
But in downtown Washington, tensions rose after dark as scores of pro-Trump "Proud Boys" protesters and "Antifa" counterprotesters faced off, separated by police in riot gear and on bicycles.
Around 200 members of the Proud Boys, a violent far right group, had joined the marches earlier on Saturday near the Trump hotel. Many wore combat fatigues and ballistic vests, carried helmets and flashed hand signals used by white nationalists.
The two groups shouted insults at each other across a street near McPherson Square and some set off fireworks, but police kept them apart, according to a Reuters reporter on the scene.
Police pepper-sprayed at least two counter-protesters before the Proud Boys left the area and regrouped several blocks away.
Protests were also planned in Georgia, Pennsylvania, Michigan, Wisconsin, Nevada and Arizona, where Trump's campaign has sought to overturn vote counts.
More than 50 federal and state court rulings have upheld Biden's victory. The U.S. Supreme Court on Friday rejected a long-shot lawsuit filed by Texas and backed by Trump seeking to throw out voting results in four states.
"Whatever the ruling was yesterday ... everybody take a deep, deep breath," retired Army General Mike Flynn, Trump's former national security adviser, told protesters in front of the Supreme Court, referring to the court's refusal to hear the Texas case.
Flynn who twice pleaded guilty to lying to the FBI about contacts with the former Russian ambassador, spoke in his first public address since Trump pardoned him on Nov. 24.
"My charge to you is to go back to where you are from" and make demands, Flynn told the crowd, without being more specific. The U.S. Constitution is "not about collective liberty it is about individual liberties, and they designed it that way," he said.
Trump has refused to concede defeat, alleging without evidence that he was denied victory by massive fraud. On his way to Andrews Air Force Base and then the Army-Navy football game in New York, Trump made three passes in the Marine One helicopter over the cheering protesters.
Trump's supporters carrying flags and signs made their way in small knots toward Congress and the Supreme Court through downtown Washington, which was closed to traffic by police vehicles and dump trucks.
Few of the marchers wore masks, despite soaring COVID-19 deaths and cases, defying a mayoral directive for them to be worn outside. Several thousand people rallied in Washington, fewer than during a similar protest last month.
As some in the crowd echoed far right conspiracy theories about the election, a truck-pulled trailer flew Trump 2020 flags and a sign reading "Trump Unity" while blaring the country song "God Bless the U.S.A."
"It's clear the election has been stolen," said Mark Paul Jones of Delaware Water Gap, Pennsylvania, who sported a tricorner Revolutionary War hat as he walked toward the Supreme Court with his wife.
Trump "is being railroaded out of office," he said, adding that Biden won with the complicity of the Supreme Court, FBI, Department of Justice and CIA. The Supreme Court "didn't even take the time to hear the case," Jones said.
Eddy Miller of Philadelphia, who was selling Trump campaign T-shirts, said he was sure "there was fraud despite what I see on the news" about court rulings striking down fraud allegations.
BATTLE OF JERICHO
Some protesters referenced the Biblical miracle of the battle of Jericho, in which the walls of the city crumbled after soldiers and priests blowing horns marched around it.
In his speech, Flynn told the protesters they were all standing inside Jericho after breaching its walls.
Ron Hazard of Morristown, New Jersey, was one of five people who stopped at the Justice Department to blow shofars - a ram's horn used in Jewish religious ceremonies - to bring down "the spiritual" walls "of corruption."
"We believe what is going on in this county is an important thing. It's a balance between biblical values and anti-biblical values," Hazard said.
His small group, including one member who wore a Jewish prayer shawl known as a tallit, are Christians "who love the Jewish people. We love Israel," he said. (Reporting by Jonathan Landay; Additional reporting by Timothy Gardner and David Lawder; Editing by Heather Timmons, Tom Brown and Daniel Wallis)
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