Trump refuses to commit whether he will accept poll results

"I will look at it at the time. I'm not looking at anything now," the controversial 70-year-old Republican candidate said in response to a question whether he would

accept the poll results, during the third presidential debate at the University of Nevada.

"I will tell you at that time. I will keep you in suspense," he said in the primetime debate that lasted for nearly 90 minutes, reiterating that the current elections are rigged.

"The media is so dishonest and so corrupt and the pile on is so amazing, The New York Times wrote an article about it. They don't even care, it's so dishonest, they've poisoned the minds of the voters, but unfortunately for them, I think the voters are seeing through it," he said.

Trump's comments at the Las Vegas showdown marked a stunning moment that has never been seen in the weeks before a modern US presidential election, CNN said.

"The stance threatens to cast doubt on one of the fundamental principles of American politics - the peaceful, undisputed transfer of power from one president to a successor who is recognized as legitimate after winning an election," it said.

Trump's remarks came after moderator Chris Wallace of Fox News said the peaceful transfer of power, a hallmark of American democracy, depends on the losing candidate accepting the validity of the electoral results.

Democratic nominee, Clinton, described her rival's refusal to accept the outcome of the election as 'horrifying', and even went so far as to paint him as a 'puppet' of Russian president Vladimir Putin.

"He is denigrating and he is talking down our democracy," the 68-year-old former secretary of state said.

"And I, for one, am appalled that someone who is the nominee of one of two major parties would take that position."

"Every time Donald thinks things are not going in his direction, he claims whatever it is is rigged against him," said Clinton, adding that he has, at various times, accused the FBI, Republican primary process and judicial system of being corrupt.

"That is not the way our democracy works. We've been around for 240 years. We've had free and fair elections. We've accepted the outcomes when we may not have liked them. That is what must be expected of anyone standing on a debate stage during a general election."

Trump, meanwhile, said American voters are wise enough to see through everything.

The bad blood between the two was unmistakable throughout their final head-to-head – and pointedly there was no handshake before or after the contest.

According to CNN, Clinton emerged as winner in the debate with an impressive 13 percentage points lead.

Overall 52 per cent of those who watched the debate said Clinton did the best job, while 39 per cent said Trump was the winner, CNN said, releasing the results of its unscientific poll.

Clinton has won all the three presidential debates. But the network noted that the victory margin was narrowest for Clinton in the third and final debate.

She won the first debate in New York by 35 point margin and the second debate in St Louis with 23 points.

During the debate, Trump accused Clinton campaign of orchestrating a series of accusations by women who said the businessman made unwanted sexual advancements.

"She should not be allowed to run. And just in that respect, I say it's rigged, because she should never have been allowed to run for the presidency based on what she did with e-mails and so many other things," Trump said during the debate to woo undecided American voters.

The bad blood between the candidates was unmistakable throughout their final head-to-head – and pointedly there was no handshake before or after the contest.

Asked about the nine women who have come forward to accuse Trump of the sexually predatory behavior he bragged about in a 2005 video leaked earlier this month, Trump insisted they were all seeking '10 minutes of fame'.

"Those stories are all totally false – I have to say that," Trump said.

"And I didn’t even apologise to my wife who is sitting right here because I didn’t do anything."

Trump called Clinton 'such a nasty woman' after she attacked his personal record on paying no income tax for years.

Trump, under enormous pressure to halt Clinton’s steady rise in opinion polls, came across as repeatedly frustrated as he tried to rally conservative voters with hard-line stands on illegal immigration, abortion rights and gun laws.

The two accused each other of not being fit to be the president of the country.

Clinton said that Trump is the 'most dangerous person to run for presidency'.

Trump is "unfit (to be president, and he proves it every time he talks," Clinton alleged.

"No, you are the one that's unfit," Trump responded by interrupting her remarks.

Trump also slammed the foreign policy of outgoing US President Barack Obama and Hillary Clinton in Iraq and Syria.

Clinton was repeatedly forced to defend her long service in government, which Trump charged had yielded no real accomplishments.

Trump portrayed himself as a candidate who would protect

the second amendment right to keep and bear arms.

Trump spoke in stark terms about immigration. He promised to stem what he characterised as an avalanche of people and heroin coming across the border, which he said was 'poisoning the blood' of young Americans.

Trump reiterated his call for a wall on the US-Mexico border and saying of his plans to deport undocumented immigrants: “We have some bad hombres here that were going to get them out.”

Clinton reiterated her position of allowing undocumented immigrants to come out of the shadows, and mocked Trump for failing to mention his signature wall during his meeting with the Mexican president Enrique Peña Nieto over the summer.

She said that there were 'undocumented immigrants in America who are paying more federal income tax than a billionaire'.