Election officials across the US say they fear for their staff’s safety amid threats and harassment from protesters, spurred by Donald Trump’s claims of a corrupt election.
It comes as Facebook removed a fast-growing group in which Trump supporters posted threats of violence.
The “Stop The Steal” group, which called for “boots on the ground to protect the integrity of the vote”, was gaining a thousand new members every 10 seconds and had grown to 365,000 members in a day.
“The group was organised around the delegitimisation of the election process, and we saw worrying calls for violence from some members,” a Facebook spokeswoman said.
While the protests outside counting stations have so far not been violent or very large, local officials were distressed by the harassment of election staff.
Michigan’s attorney general Dana Nessel tweeted a plea to “stop making harassing & threatening calls” to her staff.
“Asking them to shove sharpies in uncomfortable places is never appropriate & is a sad commentary on the state of our nation,” wrote Ms Nessel, a Democrat.
She was referring to a false conspiracy theory that Trump supporters were told to fill out ballots with Sharpie markers instead of regular pens so that their votes would not be counted by the machines.
Arizona secretary of state Katie Hobbs told CNN her main concern was staff safety but that sheriff’s deputies were providing protection.
She said protesters were “causing delay and disruption and preventing those employees from doing their job”.
On Thursday, around 100 Trump supporters gathered again in front of the Maricopa County election centre in Phoenix, some carrying military-style rifles and handguns. Arizona law allows people to openly carry guns.
Authorities at the centre used fences to create a “freedom of speech zone” and keep the entrance to the building open.
The crowd took turns chanting “count the votes” and “four more years”, and complained through a megaphone about the voting process.
Some briefly chased a man who held up a sign depicting the president as a Nazi pig behind a stage where right-wing talk-radio host Alex Jones was speaking.
“They are trying to steal the election, but America knows what happened and it’s fighting back,” Jones told the crowd.
“1776 is the answer to 1984,” he said, an apparent reference to the US Declaration of Independence and the dystopian George Orwell novel.
The group paused to listen as Mr Trump spoke from the White House, where he repeated many of his groundless assertions of a rigged vote.
They whooped and clapped when the president said: “We’re on track to win Arizona.” However, Mr Biden is still in the lead there, albeit by a small margin of more than 47,000 votes.
Both sides held rallies in Philadelphia on Thursday, where election staffers slowly counted thousands of mail-in ballots
that could decide Pennsylvania’s crucial 20 Electoral College votes.
Trump activists waved flags and carried signs saying: “Vote stops on election day” and “sorry, polls are closed” as Biden supporters danced to music behind a barricade across the street.
Late on Thursday, Philadelphia police said they were investigating an alleged plot to attack the city’s Pennsylvania Convention Center, where votes were being counted.
Police took at least one man into custody and seized a weapon. No injuries were reported.
In Atlanta, roughly 100 chanting Trump supporters gathered outside State Farm Arena as votes were being counted. Several Atlanta police officers monitored the scene.
Tom Haas, 50, who said he was visiting Atlanta from Chicago on business, said he was convinced Mr Trump had won the election.
“There’s obvious voter fraud, and it’s coming out of the larger Democratic-run cities,” he said. “Atlanta is one of them.”
“Our democracy is under attack,” he said, echoing Mr Trump’s language.
A few dozen Trump supporters gathered outside Detroit’s convention centre on Thursday morning as election workers counted absentee ballots inside.
The protesters held signs that read, “stop the steal” and “stop the cheat”.
In Las Vegas, around 100 backers of the president chanted as they stood along the road in front of the election offices.
In Milwaukee, some 50 Trump supporters gathered in front of a city building where votes were being counted, blasting country music, waving flags and carrying signs reading “recount” and “rigged”.
Roughly a dozen counter-protesters arrived after an hour, shouting “black lives matter” and “say their names”, referring to the victims of police brutality.
Others threw eggs at the Trump supporters from a passing car.
“My country’s future is what brings me out here tonight,” said Mitchell Landgraf, a 21-year-old construction worker who cast his first vote in a presidential election for President Trump. “I’m afraid if it goes one way that this country will go downhill fast.”
Mr Trump’s campaign has called for a recount in Wisconsin, where Mr Biden has been declared the winner by a razor-thin margin.