Dozens of supporters of US President Donald Trump chanting “Stop the count!” descended on a vote-tallying centre in Detroit on Wednesday local time.
The Detroit protests started shortly before AP declared Mr Biden had won the state of Michigan.
Another vocal pro-Trump group descended on Phoenix, with Joe Biden holding a narrow lead in the crucial state of Arizona.
Video shot by local media showed angry people gathered outside the TCF Center and inside the lobby, with police officers lined up to keep them from entering the counting area.
They chanted “Stop the count!” and “Stop the vote!”
Earlier, the Republican campaign filed a lawsuit in a bid to stop the count, demanding Michigan’s Democratic secretary of state allow in more inspectors.
Mr Trump has repeatedly insisted without evidence that there are major problems with the voting and the counting.
Michigan Attorney-General Dana Nessel, a Democrat, insisted both parties and the public had been given access to the tallying “using a robust system of checks and balances to ensure that all ballots are counted fairly and accurately”.
National Guard called in Portland
In Portland, Oregon, Governor Kate Brown activated the National Guard after demonstrators engaged in what authorities said was widespread violence downtown, including smashing windows.
The city has been a scene of regular protests for months.
Protesters were demonstrating about a range of issues, including police brutality and the counting of the vote.
“To cast doubt on this election has terrible consequences for our democracy and I’m worried about what’s going to come in the next days and weeks and months,” said anti-Trump protester Richard March.
Hundreds in California urge state officials to ‘count every vote’
Two hundred people gathered at Oakland City Hall on Wednesday to urge state officials to “count every vote”‘, after Mr Trump called for a halt to ballot tabulations with the election outcome still unsettled.
Jose Bernal, 32, an organiser with the Ella Baker Center for Human Rights, said he was terrified of what might happen in the aftermath of Tuesday’s election, which pitted Mr Trump against Democratic rival Joe Biden.
“We are one community, we’re going to stand strong and we’re going to defend every bit of democracy that we have left. That is what we want to do here. That is the aim for us,” he said.
“Our interest today is to count every vote. Support democracy. Count every vote,” said Mary Foran, who voted for Mr Biden.
In Poway, north-east of San Diego, a small group gathered by the side of the road waving placards reading “Count every vote” and “Every vote counts”.
Chicago protesters call for Trump to go
A group of demonstrators marched through downtown Chicago on Wednesday night, demanding Mr Trump concede the presidential election.
At least 100 people marched north on Michigan Avenue, carrying signs and large banners reading “Count every vote” and “Out now!”
The demonstration came a day after Mr Trump falsely and prematurely declared victory in the race and later filed a number of lawsuits to stop the ballot counting in a few key states.
Boston protesters call for all votes to be counted
The Boston Globe newspaper reported that hundreds of protesters had gathered across the city on Wednesday to demand every vote is counted.
The organisers reportedly said the rallies were not in reaction to either candidate.
But many demonstrators in downtown Boston directed anger at Mr Trump, carrying placards and chanting slogans such as “No justice, no peace”.
Protesters gathered for a rally in the Boston neighbourhood Roxbury, where speakers criticised the US electoral system and political power structures.
“No matter how many times I smashed that refresh button last night, I did not feel refreshed, I did not feel relieved,” Blaze Travis, a 27-year-old Roxbury resident the Boston Globe reported as telling the crowd.
While many businesses near Copley Square had reportedly boarded up windows, rally organisers told local TV station 7 News that they wanted the protest to be peaceful and to “not engage with the police”.
Scattered protests from Washington DC to Seattle
On Tuesday night, scattered protests broke after voting ended, stretching from Washington DC to Seattle, but there was no widespread unrest or significant violence.
In Portland, Oregon, Richard March came to an anti-Trump protest despite a heart condition that makes him vulnerable to COVID-19.
“To cast doubt on this election has terrible consequences for our democracy,” he said.
“I think we are a very polarised society now — and I’m worried about what’s going to come in the next days and weeks and months.”
Other anti-Trump demonstrations saw protesters gathering in New York City, Houston, Minneapolis and other cities.
