A man is facing a murder charge after a car ploughed into a crowd of people protesting against a white supremacist rally in Virginia, killing a 32-year-old woman and injuring more than a dozen others, on a day full of violent confrontations.

Shortly after the incident, a Virginia State Police helicopter above the rally crashed outside Charlottesville, killing the pilot and a trooper.

The chaos boiled over at what is believed to be the largest group of white nationalists to come together in a decade, protesting against plans to remove a statue of Confederate general Robert E Lee.

That gathering sparked a counter-demonstration by others protesting against racism.

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Virginia governor Terry McAuliffe declared an emergency and police in riot gear moved people away.

Matt Korbon, 22, a University of Virginia student, said several hundred counter-protesters were marching when "suddenly there was just this tyre screeching sound".

A silver Dodge Challenger smashed into another car, then reversed, barrelling through "a sea of people".

The impact hurled people into the air and those left standing scattered, screaming and running for safety.

The driver was later identified by police as James Fields, 20, of Ohio.

He has been charged with second-degree murder, three counts of malicious wounding, and one count related to leaving the scene. A bail hearing will take place on Monday.

US president Donald Trump condemned "in the strongest possible terms" what he called an "egregious display of hatred, bigotry and violence on many sides" after the clashes and called for "a swift restoration of law and order and the protection of innocent lives".

He said he and Mr McAuliffe "agreed that the hate and the division must stop and must stop right now".

Field's mother, Samantha Bloom, said she knew her son was attending a rally in Virginia but did not know it was a white supremacist event.

"I thought it had something to do with Trump. Trump's not a white supremacist," she said.

"He had an African-American friend so ...," she said before her voice trailed off. She added that she would be surprised if her son's views were that far right.

Ms Bloom, who became visibly upset as she learned of the injuries and deaths at the rally, said she and her son had just moved to the Toledo area from the northern Kentucky city of Florence, where Fields grew up.

She said she relocated to Ohio for work.

The Department of Justice has opened a federal civil rights investigation into the deadly car attack.

Attorney general Jeff Sessions said that the FBI's Richmond field office and Rick Mountcastle, the US Attorney for the Western District of Virginia, would lead the investigation.

"The violence and deaths in Charlottesville strike at the heart of American law and justice," Mr Sessions said.

"When such actions arise from racial bigotry and hatred, they betray our core values and cannot be tolerated."

The turbulence began on Friday night, when the white nationalists carried torches though the University of Virginia campus.

It quickly spiralled into violence Saturday morning. Hundreds of people threw punches, hurled water bottles and unleashed chemical sprays.

Authorities said the car collision left 19 people injured and a total of 35 patients were treated.

State police said the helicopter was "assisting public safety resources with the ongoing situation" when it crashed in a wooded area.

The pilot, Lieutenant Jay Cullen, 48, of Midlothian, Virginia, and Trooper-Pilot Berke Bates of Quinton, Virginia, died at the scene.

Some of the white nationalists cited Mr Trump's election victory as validation for their beliefs and Trump critics pointed to the president's rhetoric as exploiting America's festering racial tension.

The Rev Jesse Jackson noted that for years Mr Trump publicly questioned former president Barack Obama's citizenship.

"We are in a very dangerous place right now," he said.

Right-wing blogger Jason Kessler had called for what he termed a "pro-white" rally in Charlottesville, sparked by the monument decision and both white nationalists and their opponents promoted the event for weeks.

But many were just locals caught in the fray.

Teacher Colleen Cook, 26, who stood on a kerb shouting at demonstrators to go home, said she sent her son, who is black, out of town for the weekend.

"This isn't how he should have to grow up," she said.

Cliff Erickson said he thought removing the statue amounted to erasing history and the "counter-protesters are crazier than the alt-right".

"Both sides are hoping for a confrontation," he said.

It is the latest hostility in Charlottesville since the city, about 100 miles from Washington DC, voted earlier this year to remove a statue of Lee.

In May, a torch-wielding group that included prominent white nationalist Richard Spencer gathered around the statue for a night-time protest, and in July, about 50 members of a North Carolina-based Klu Klux Klan group travelled there for a rally, where they were met by hundreds of counter-protesters.

Charlottesville, nestled in the foothills of the Blue Ridge Mountains, is a liberal-leaning city that is home to the flagship University of Virginia and Monticello, the home of Thomas Jefferson.