Trump claims US election results rigged 'at many polling places'

Republican presidential nominee Donald Trump made efforts to cast doubt on the legitimacy of the US election, saying on Twitter on Sunday that he believed the results were being "rigged" at many polling places.

His tweet came hours after his vice presidential running mate, Mike Pence, said Republicans would accept the outcome of the 8 November contest between Trump and his Democratic rival, Hillary Clinton.

"The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places - SAD," Trump wrote on Twitter, in the latest of a series of comments he has made over the past several days calling into question the fairness of the election.

The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places - SAD

— Donald J. Trump (@realDonaldTrump) October 16, 2016

Trump, who is trailing Clinton in opinion polls, did not provide any evidence to back his allegations of impropriety at the voting booth.

Early voting and voting by mail have begun in many states.

In another tweet later on Sunday, 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."

"Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning," Trump tweeted.

Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning @NCGOP

— Donald J. Trump (@realDonaldTrump) October 16, 2016

Clinton denounced the attack as "horrific and unacceptable" in her own tweet, adding: "Very grateful that everyone is safe.