Thousands of Donald Trump supporters alleging electoral fraud converged on several US cities and towns on Saturday and there were isolated scuffles with counter-demonstrators.
In Washington DC, more than 20 people were arrested and four people were stabbed, police said.
Mr Trump lost the 3 November election to Joe Biden but is yet to concede.
The Electoral College, the system which elects US presidents, is due to endorse Mr Biden’s victory on Monday.
Mr Biden won 306 votes to Mr Trump’s 232 in the Electoral College, and gained over seven million more votes than his Republican rival in the popular vote.
In the nation’s capital, police sought to keep the two sides apart, a strategy that included sealing off Black Lives Matter Plaza where counter-demonstrators had gathered.
Pro-Trump demonstrators, rallying under the banner of “Stop the Steal”, were joined by members of the far-right Proud Boys, dressed in yellow and black, many wearing bullet-proof vests.
Mr Trump caused controversy by saying the group should “stand back and stand by” during a September presidential debate, though he later condemned “all white supremacists”.
As night fell, Proud Boys and antifa counter-demonstrators, mostly separated by police lines, yelled insults at each other. But sporadic violence broke out.
The stabbings took place near the downtown Harry’s Bar, but it was not clear which group those injured belonged to, according to the Washington Post.
Rallies also took place in Olympia, the capital of Washington state, Atlanta and St Paul, Minnesota. Police in Olympia said one person had been shot and three arrested as rival groups clashed.
The Washington DC rally attracted several thousand Trump-supporters but it was smaller than a similar event on 14 November. Few participants wore masks despite Covid-19 restrictions.
There were speeches by Mr Trump’s now pardoned former National Security Advisor, Michael Flynn, and Sebastian Gorka, another former White House official.
General Flynn likened the protesters to soldiers and priests breaching the walls of Jericho, echoing the rally organisers’ call for “Jericho Marches” to overturn the election result.
Mr Gorka urged the president not to give up his legal campaign – based on debunked allegations of electoral fraud – to reverse the election result.