A planned protest by white nationalists in Charlottesville, Virginia, will be the "largest hate gathering of its kind in decades in the United States," a monitoring group has said. Hundreds of right-wing activists are expected to attend the "Unite the Right" meeting on Saturday 12 August to demonstrate against the removal of a Confederate-era statue in a local park.

The Southern Poverty Law Center (SPLC), a US non-profit which monitors "hate groups", has warned the rally will draw far-right extremists from across the country, including neo-Nazis, white supremacists, and Ku Klux Klan (KKK) members.

They are expected to be met by counter-demonstrators from left-wing and civil rights groups – including Antifa and Black Lives Matter – with state police in riot gear to be deployed to prevent violence.

"This is the biggest rally event we've had this millennium," white nationalist Brad Griffin is reported as saying on a recent radio showed hosted by former KKK leader David Duke.

He said his movement's activists "get hung up on interacting with people online," and that the message board culture of right-wing activism had created "a lot of paranoia when people don't know each other in real life."

But the Unite the Right rally will give "the movement a real world presence, which it hasn't had in 15 years," Griffin said.

White nationalist Richard Spencer, often credited with being the founder of the so-called Alt-Right movement, is among those due to speak at this weekend's demonstration, along with fellow Alt-Right activist Tim Gionet.

The SPLC said the event may well become a "seminal point for the Alt-Right and the extremist hate fringe". It added: "It's a bold move beyond the anonymity of web sites, message boards, pseudonyms and social media — a move to take the hardcore, racist, white nationalist message to the public square."

Nearly 700 people have signed up to attend the Unite the Right rally, according to its Facebook page. It was originally scheduled for noon on Saturday at what organisers continue to call "Lee Park", a city landmark which was officially renamed Emancipation Park.

It is the site of a statute of Confederate War General Robert E. Lee that city officials controversially voted to remove in April – a decision that has since prompted several demonstrations by right-wing groups in the city.

But the upcoming rally hit a snag this week after Charlottesville City Council officials revoked the permit to hold the demonstration in Emancipation Park due to what they said were safety concerns. It instead said the rally should be held in a larger park a mile away.

Following complaints from the rally's organisers, the American Civil Liberties Union (ACLU) called for the decision to be reversed, saying it raised "a number of serious First Amendment concerns".

Some supporters trying to attend the demonstration have also found themselves unable to find accommodation for the weekend after rental company Airbnb removed activists from the site.

A spokesperson for Airbnb said users had been banned because their behaviour was deemed "antithetical to the Airbnb Community Commitment". The company went on to highlight its guidelines stating that "those who are members of the Airbnb community accept people regardless of their race, religion, national origin, ethnicity, disability, sex, gender identity, sexual orientation, or age."

Organiser Jason Kessler called the decision "outrageous", saying it "should be grounds for a lawsuit".

"It's the racial targeting of white people for their ethnic advocacy," he told the Washington Post. Kessler said the rally "is opposed to the historical and demographic displacement of white people. Would Airbnb cancel the service of black nationalists or Black Lives Matter activists for their social media activity? Of course not."

unite the right
The Ku Klux Klan protests on 8 July, 2017 in Charlottesville, Virginia against the planned removal of a statue of General Robert E. Lee, and calling for the protection of Southern Confederate monuments.Chet Strange/Getty Images