U.S. authorities opened an investigation into the deadly violence in Virginia, which put renewed pressure on the Trump administration to take an unequivocal stand against right-wing extremists occupying a loyal segment of the Republican president's political base.

A 32-year-old woman was killed and 19 people were injured, five critically, on Saturday when a man plowed a car into a crowd of people protesting the white nationalist rally in the Southern college town of Charlottesville. Another 15 people were injured in bloody street brawls between white nationalists and counter-demonstrators who fought each other with fists, rocks and pepper spray.

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Two Virginia state police officers died in the crash of their helicopter after assisting in efforts to quell the unrest, which Mayor Mike Signer said was met by the presence of nearly 1,000 law enforcement officers.

Former U.S. Army enlistee James Alex Fields Jr., 20, a white Ohio man described by a former high school teacher as having been "infatuated" with Nazi ideology as a teenager, was due to be appear in court on murder and other charges stemming from the deadly car crash.

The federal "hate crime" investigation of the incident "is not limited to the driver," a U.S. Justice Department official told Reuters. "We will investigate whether others may have been involved in planning the attack."

Democrats and Republicans criticized Trump for waiting too long to address the violence - his first major crisis on the domestic front that he has faced as president - and for failing when he did speak out to explicitly condemn white-supremacist marchers who ignited the melee.

Trump on Saturday initially denounced what he called "this egregious display of hatred, bigotry, and violence on many sides."

On Sunday, however, the White House added: "The president said very strongly in his statement yesterday that he condemns all forms of violence, bigotry, and hatred, and of course that includes white supremacists, KKK, neo-Nazi, and all extremist groups. He called for national unity and bringing all Americans together."

The statement was emailed to reporters covering Trump at his golf resort in New Jersey and attributed to an unidentified "White House spokesperson."

REUTERS