Trump denounces racism as 'evil'; hits out at white supremacists, neo-Nazis

US President Donald Trump on Monday denounced racism as "evil" as he slammed white supremacist and neo-Nazi groups for the weekend violence in Charlottesville, describing them as "criminals and thugs".

All those who engaged in racist violence over the weekend in Charlottesville "will be held fully accountable," Trump said in a televised address from the White House.

"We will spare no resource in fighting so every American child can grow up free from violence and fear," Trump said in his remarks that lasted for a few minutes.

He did not take any shouted questions from the pool of reporters at the White House.

Hundreds of white supremacists clashed with counter demonstrators as a car rammed into the crowd and a police helicopter crashed on Saturday, killing three people and injuring 19 others in Charlottesville, Virginia.

"Racism is evil. And those who cause violence in its name are criminals and thugs, including the KKK, neo-Nazis, white supremacists, and other hate groups that are repugnant to everything we hold dear as Americans," Trump said.

The Department of Justice, he said, has opened a civil rights investigation into the deadly car attack that killed one innocent American, and wounded others.

"To anyone who acted criminally in this weekend's racist violence, you will be held fully accountable. Justice will be delivered," he said.

"We condemn in the strongest possible terms this egregious display of hatred, bigotry and violence. It has no place in America," said the US President.

Observing that those who spread violence in the name of bigotry strike at the very core of America, he said two days ago a young American woman, Heather Heyer, was tragically killed.

"Her death fills us with grief, and we send her family our thoughts, our prayers and our love," Trump said. He also mourned the death of two Virginia state troopers in the helicopter crash near the protest site.

As a candidate, Trump said, he promised to restore law and order to the country.

"Our federal law enforcement agencies are following through on that pledge. We will spare no resource in fighting so that every American child can grow up free from violence and fear," he said.

"We will defend and protect the sacred rights of all Americans, and we will work together so that every citizen in this blessed land is free to follow their dreams, in their hearts, and to express the love and joy in their souls," Trump said.

Earlier, Trump had condemned the violence but said "many sides" were involved, inviting criticism from across the political spectrum for not specifically denouncing the far right.