Officials in Charlottesville in the US state of Virginia have declared a state of emergency ahead of a large march by white nationalists.
Thousands of people are expected to join the “Unite the Right” rally against plans to remove a statue of a pro-slavery US Civil War general.
Violent clashes between far-right groups and counter-protesters have left at least two injured, police say.
President Donald Trump has condemned the violence.
On Twitter, he said: “We ALL must be united & condemn all that hate stands for. There is no place for this kind of violence in America. Lets come together as one!”
After the clashes subsided, a car rammed into a crowd of counter-protesters. It was not immediately clear how many people had been injured.
Earlier, police fired tear gas against demonstrators and said that arrests had been made after a declaration of unlawful assembly at Emancipation Park.
The state of emergency allows local authorities to request additional resources if needed, the police department said.
The far-right protesters, some waving Confederate flags, carrying shields and wearing helmets, are angry about the planned removal of a statue of Gen Robert E Lee from Charlottesville. Gen Lee commanded the Confederate forces in the US Civil War of 1861-65.
The New York Times reports that some of them were chanting “You will not replace us,” and “Jew will not replace us.”
Anti-racism organisations such as Black Lives Matter have also held marches.
At the scene: Bottles thrown
By Joel Gunter, BBC News, Charlottesville
There were very violent scenes at Emancipation Park and it took some time for the police to intervene.
Both sides were throwing bottles and rocks and using pepper spray.
The far-right protesters were a mix of different groups with shields and batons and the declaration of a state of emergency seemed to have had a significant impact on them, as they started to dissipate.
Riot police have been deployed, but tensions remain high, with people screaming at each other and demonstrators still out on the streets.
Shiquan Rah, a 21-year-old demonstrator who had joined the counter-protest said about the far-right groups: “These people don’t have a message, their message is hate and violence. This is a spiritual war we’re in.
Virginia Governor Terry McAuliffe urged calm tweeting: “The acts and rhetoric in #Charlottesville over past 24 hours are unacceptable [and] must stop. A right to speech is not a right to violence.”
First Lady Melania Trump also condemned the violence, saying on Twitter: “Our country encourages freedom of speech, but let’s communicate [without] hate in our hearts. No good comes from violence.”
Charlottesville mayor Mike Signer had earlier called the rally a “parade of hatred, bigotry, racism and intolerance”.
US Civil War and alt-right links
- 1861-65 US Civil War between the northern and southern states was principally caused by slavery
- Southern Confederate forces, which backed slavery, eventually surrendered to Union army and slavery was abolished
- A number of cities have grappled with Confederate symbols that still exist today, with flags and monuments becoming key venues for alt-right groups in recent months
- Supporters say Confederate symbols represent freedom and liberty, but opponents say their roots are in slavery
- The alt-right is a disparate group of provocateurs who hate political correctness and love Donald Trump, but critics say they are bigoted white nationalists
On Friday, the white nationalists held lit torches – which some observers described as a reference to the Ku Klux Klan – and chanted “White lives matter” as they marched through the University of Virginia in the city.
Charlottesville is considered a liberal college town – and 86% of the county voted for Hillary Clinton in last year’s presidential elections.
However, the town has become a focal point for white nationalists after the city council voted to remove a statue of Gen Lee.
Some observers also argue that Mr Trump’s election to the White House re-energised the far right across the US.