The City of Boston is making preparations for a conservative rally scheduled for Saturday on Boston Common, following the eruption of violence in Charlottesville, Va., that has raised troubling questions about the rise of extremists’ views across the country.

After a woman was killed when a car rammed a crowd of counterprotesters and others were injured, Twitter and Facebook exploded with postings about a rally next weekend in Boston that they say might attract white supremacists. Organizers were spreading information about the rally on Facebook, urging supporters to gather from noon to 5 p.m. Saturday on the nation’s oldest park for a Boston Free Speech rally.

The mayor and Boston police sought on Sunday to reassure residents that violence would not be tolerated in the city.