A Republican party office in North Carolina was firebombed overnight and a nearby building was scrawled with graffiti warning "Nazi Republicans" to "leave town or else," authorities said Sunday.

In a statement, authorities in Hillsborough, northwest of Durham, said that no one was injured in the apparent attack on the Orange County Republican Party headquarters.

A bottle containing a flammable substance was thrown through a front window, where it ignited and damaged furniture and the office's interior, the statement said, adding that the fire went out on its own.

The graffiti, which included a swastika, was painted on an adjacent building, the statement said.

A nearby business owner discovered the damage at 9 a.m. Sunday.

"This highly disturbing act goes far beyond vandalizing property," said Hillsborough Mayor Tom Stevens, according to the statement. "It willfully threatens our [community's] safety via fire, and its hateful message undermines decency, respect and integrity in civic participation. I believe I speak for the overwhelming majority of people who make Hillsborough their home: Acts like this have no place in our community."

North Carolina Republican Party spokeswoman Emily Weeks told NBC News that the office is totally unusable and that materials inside, possibly including completed absentee ballots, may have been destroyed.

Additional security would be requested for all GOP offices and events around the state until Nov. 8, Woodhouse said

She said the office had received no threats.

In a statement, the state GOP executive Dallas Woodhouse called the incident a hate crime and said that "all Americans should be outraged" by this "violent attack against our democracy."

Hillary Clinton's campaign also condemned the incident as "horrific and unacceptable," adding their gratitude that no one was hurt.