In a tweet on Sunday, Republican nominee Donald Trump blamed "animals representing Hillary Clinton" and Democrats in North Carolina for an overnight attack on a local Republican Party headquarters in that state.
Local authorities said the building in Hillsborough, North Carolina, had been struck through a front window with flammable material and an adjacent building wall was spray-painted with a swastika and the words "Nazi Republicans leave town or else."
"The flammable substance appears to have ignited inside the building, burned some furniture and damaged the building's interior before going out," a statement from local authorities said.
"Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning," Trump tweeted.
Clinton denounced the attack as "horrific and unacceptable" in her own tweet, adding: "Very grateful that everyone is safe.