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 erupted between far-right groups and counter-protesters who have also gathered in the city.
At least two people have been injured, police say.
Police have 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.
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.”
The BBC’s Joel Gunter in Charlottesville says police have not yet interrupted clashes between the rival demonstrators, adding that it had been “extremely violent” so far.
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.”
US 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”.
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 US President Donald Trump’s election to the White House re-energised the far right across the US.