Donald Trump has blamed "animals representing Hillary Clinton" for an apparent firebomb attack on one of the Republican's campaign offices.

The presidential candidate took to Twitter after the office in Orange County, North Carolina, had been damaged when a petrol bomb was thrown through a window.

The walls of the office were charred and a sofa burned in the attack, but no one was hurt.

Graffiti reading “Nazi Republicans leave town or else” was sprayed on a nearby building, along with a swastika.

Mr Trump immediately blamed Hillary Clinton's supporters, tweeting: “Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning”.

He added “All safe in Orange County, North Carolina. With you all the way, will never forget. Now we have to win. Proud of you all!”

Mrs Clinton condemned the attack, calling it “horrific and unacceptable”. She said she was “very grateful that everyone is safe”.

The North Carolina Republican Party account thanked her for her "thoughts and prayers".

Sources said it was lucky no one was harmed in the attack, as the firebomb reportedly landed near a sofa where campaign volunteers often take naps.

Dallas Woodhouse, the Republican Party’s executive director in the state, told The Charlotte Observer the attack was “political terrorism”.

“The office itself is a total loss,” he said “The only thing important to us is that nobody was killed, and they very well could have been.”

Nobody was hurt in the incident and police are investigating (WNCT)

The state governor, Pat McCrory, called it “an attack on our democracy”.

Mr Trump’s claims that the attack was carried out because he is winning comes as a new poll suggests his Democrat rival has a 11 point lead across the country. Polls also suggest Mrs Clinton is ahead in the battleground state of North Caronlina, where the attack took place.

The nationwide NBC/Wall Street Journal poll showed Mrs Clinton has the support of 48 per cent of voters compared to Mr Trump’s 37 per cent. Libertarian Gary Johnson receives 7 per cent while the Green Party’s Jill Stein is estimated to be on 2 per cent.

Experts suggested the huge gap - significantly greater than the margin by which Barack Obama beat John McCain in 2008 - would be difficult for Mr Trump to overcome before the November 8 election.

"Donald Trump's chances of winning this election have faded," said Fred Yang of Hart Research Associates, which conducted the survey.

"This poll is showing the writing on the wall".

What did Donald Trump say during the second presidential debate? Show all 8 1 /8 What did Donald Trump say during the second presidential debate? What did Donald Trump say during the second presidential debate? On the leaked tape from 2005 where he talks about sexually assaulting women “I'm very embarrassed by it, I hate it, but it's locker room talk. It's one of those things. I will knock the hell out of Isis” Getty What did Donald Trump say during the second presidential debate? On Hillary Clinton “I hate to say it but if I win I'm going to instruct my attorney general to get a special prosecutor to look into your situation. There has never been so many lies, so much deception. You ought to be ashamed of yourself.” Rex What did Donald Trump say during the second presidential debate? On Bill Clinton “What he's done to women, there's never been anybody in the history of politics in this nation that's been so abusive to women.” AP What did Donald Trump say during the second presidential debate? On whether his alleged opposition to Iraq War had been disproven "It’s not debunked. It’s not debunked." Getty What did Donald Trump say during the second presidential debate? On exploiting tax loopholes "I absolutely used it, and so did Warren Buffett, and so did George Soros and so did many people who Hillary is getting money from." Getty What did Donald Trump say during the second presidential debate? On claims he's sexist “I have great respect for women. Nobody has more respect for women than I do.” Reuters What did Donald Trump say during the second presidential debate? On what he respects about Hillary Clinton “I will say this about Hillary - she doesn't quit, she doesn't give up. I tell it like it is. She's a fighter.” Reuters What did Donald Trump say during the second presidential debate? On his controversial immigration policies "It’s called extreme vetting. We’re going to areas like Syria, where they are coming in by the tens of thousands because of Barack Obama and Hillary Clinton wanting to allow a 550 per cent increase [of refugees] over Obama. People are coming into this country. We have no idea who they are, where they are from and what their feelings are about this country." Getty

Meanwhile Mr Trump's running mate, Mike Pence, told NBC's Meet the Press that the businessman would "absolutely accept" the election result, despite the Republican presidential candidate having claimed the vote was "rigged".

"The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary", Mr Trump had said.

It comes after a difficult week for the Trump campaign in which several women claimed they had been sexually assaulted by the billionaire.