The FBI has arrested three suspected members of a neo-Nazi hate group who planned to travel to a pro-gun rally in Virginia on Monday.
One was a Canadian army reservist who was fired in August over ties to hate groups and has been suspected missing since, Canadian police told the BBC.
Virginia governor Ralph Northam has declared a state of emergency in the city of Richmond ahead of the rally.
He said law enforcement believed there was a threat of violence.
Governor Northam on Thursday announced a ban on guns in the state's Capitol area in Richmond from Friday until Tuesday, citing threats of violence made ahead of the rally. The order also covers other weapons such as knives and sticks.
He said some of the violent rhetoric seen online was reminiscent of that seen before the deadly Charlottesville rally in 2017, at which a 32-year-old counter protester, Heather Heyer, was killed by white nationalist James Fields.
Who are the accused?
FBI in Baltimore, Maryland charged Brian Lemley, 33, and William Bilbrough, 19, with transporting and harbouring aliens. They charged Mr Lemley and Canadian Patrik Mathews with transporting a firearm and ammunition with intent to commit a felony.
The FBI alleges that Mr Mathews entered the US illegally at the Manitoba/Minnesota border. All three are accused of being members of a white supremacist group known as The Base.
According to the criminal complaint filed with the state's attorney general, The Base's members discussed in encrypted online chatrooms "recruitment, creating a white ethno-state, committing acts of violence against minority communities (including African-Americans and Jewish-Americans), the organization's military-style training camps, and ways to make improvised explosive devices".
Rally for gun rights
Monday's rally was planned by the Virginia Citizens Defence League (VCDL), a pro-gun-rights group, to protest gun control legislation that is expected to pass in the new year. VCDL said it was expecting 50,000 people to attend the protest.
We have received credible intelligence from our law enforcement agencies of threats of violence surrounding the demonstration planned for Monday, January 20. This includes extremist rhetoric similar to what has been seen before major incidents, such as Charlottesville in 2017.— Ralph Northam (@GovernorVA) January 15, 2020
Democrats won control of the Virginia state legislature last autumn, for the first time since 1994, and have made gun control a key part of their platform, especially in light of last summer's shooting at Virginia Beach, which killed 12.
Mr Northam, who is also a Democrat and has been governor since 2017, tried to get gun control measures passed to no avail this summer, before the election.
On the run
Mr Mathews was a combat engineer in the Canadian Army Reserve, but he was fired in late August after an nundercover reporter for the Winnipeg Free Press connected him to The Base and alleged he was trying to recruit new members.
"We're real (expletive) Nazis and they can't do s—- to us but wait for us to put em against the wall," Mr Mathews allegedly wrote in an online encrypted chatroom.
Police raided Mr Matthews' home shortly after the report and seized a number of firearms.
He subsequently disappeared, and RCMP were still looking for him on 2 September, when they found his car abandoned about five miles (8 km) away from the Minnesota border.