Backers of President Donald Trump, some carrying guns, ramped up demonstrations on Thursday night against what he has baselessly called a rigged election, in battleground states where votes were still being counted.
The demonstrations were largely peaceful, although Trump supporters occasionally shouted with counterprotesters. Trump says the election is being stolen but there has been no evidence of fraud.
In Arizona, one of the closely contested states in the too-close-to-call race between Trump and Democratic challenger Joe Biden, Trump and Biden supporters briefly scuffled outside the Maricopa County Elections Department in Phoenix.
Several heavily armed right-wing groups assembled on the site as election workers counted votes inside, but the protests remained mostly peaceful despite mounting tension.
In Philadelphia, police said they arrested one man and seized a weapon as part of an investigation into a purported plot to attack the city's Pennsylvania Convention Center, where votes were being counted.
But otherwise the scene in Philadelphia was less confrontational - festive, even - where pro-Trump and pro-Biden demonstrators were separated by waist-high portable barriers under a strong police presence.
With the future of the presidency in the balance, restive encounters also unfolded in New York and Washington as well as swing-state cities such as Milwaukee, Wisconsin; Las Vegas, Nevada; Detroit, Michigan; and Atlanta, Georgia.
In Phoenix, Trump supporters briefly chased a man who held up a sign depicting the president as a Nazi pig behind a stage where right-wing conspiracy theorist Alex Jones was speaking.
As mail-in ballots in Pennsylvania gave Biden lead, Philadelphia demonstrators danced. Two people wearing postal box costumes bounced to pulsating music while carrying a banner that read, "The battle isn't over." Others, backed by a live drum corps, marched behind the sign, "Union members fight to count every vote."
Trump activists waved flags and carried signs saying, "Vote stops on Election Day," and "Sorry, polls are closed." Biden backers showed their support for the civil servants who were at work inside.
In Milwaukee, some 50 Trump supporters gathered for a "Stop the Steal" rally in front of a city building where votes were being counted, blasting country music, waving flags and carrying signs reading "Recount" and "Rigged". At least one man had a gun in holster.
Roughly a dozen counterprotesters arrived later, shouting "Black lives matter" and "say their names," referring to victims of police brutality. Others threw eggs at the Trump supporters from a passing car.
At least 400 protesters gathered outside the Clark County Election Department in Las Vegas. Loud patriotic anthems blared over speakers as people waved giant Trump and American flags.