The warning specifically refers to events last week in the city of Charlottesville, Virginia, where civil rights activist Heather Heyer was killed when a car rammed into a group of people protesting against a white nationalist rally.

Such statements are usually issued by the United Nations Committee on the Elimination of Racial Discrimination (Cerd) over fears of ethnic or religious conflict. In the past decade, the only other countries issued with an early warning were Burundi, Iraq, Ivory Coast, Kyrgyzstan and Nigeria. "We are alarmed by the racist demonstrations, with overtly racist slogans, chants and salutes by white nationalists, neo-Nazis, and the Ku Klux Klan, promoting white supremacy and inciting racial discrimination and hatred," Anastasia Crickley, Chairperson of UN Committee on the Elimination of Racial Discrimination (CERD), said in a statement Wednesday.

In a decision issued under its 'early warning and urgent action' procedure, the Committee, which monitors implementation of the International Convention on the Elimination of All Forms of Racial Discrimination, stated,"There should be no place in the world for racist white supremacist ideas or any similar ideologies that reject the core human rights principles of human dignity and equality."

The United States ratified the Convention in 1994.

In addition to the criminal investigation of the individual who ploughed his car into a crowd of peaceful protestors killing a woman, the UN experts asked the US authorities to undertake concrete measures "to address the root causes of the proliferation of such racist manifestations."

"We call on the US Government to investigate thoroughly the phenomenon of racial discrimination targeting, in particular, people of African descent, ethnic or ethno-religious minorities, and migrants," Ms Crickley added.

CERD also called on the government to ensure that the rights to freedom of expression, association and peaceful assembly are not exercised with the aim of destroying or denying the rights and freedoms of others, and also asked it to provide the necessary guarantees so that such rights are not misused to promote racist hate speech and racist crimes.