Donald Trump has said the US presidential race is being "rigged by the media" in order to elect Hillary Clinton.

He made the unprecedented assertation in response to accusations of unwanted kissing, groping and more from at least eight women.

Mr Trump maintained his innocence and denounced Ms Clinton and a supposed international media conspiracy aimed at denying him the White House.

"100 percent fabricated and made-up charges, pushed strongly by the media and the Clinton Campaign, may poison the minds of the American Voter. FIX!" Mr Trump tweeted on Saturday morning.

"This election is being rigged by the media pushing false and unsubstantiated charges, and outright lies, in order to elect Crooked Hillary!" he added.

He went on to say Ms Clinton should be in jail and repeated his assertion the election looks to have been rigged.

Mr Trump called the women who accused him of sexual assault "sick," in a speech at a rally in Greensboro, North Carolina.

The Republican nominee said he had never met most of the women who had made "phony" claims about him.

"I have no idea who these women are," he told the crowd. "I have no idea. I have no idea. And I think you know I have no idea as you understand me for a lot of years, OK?"

"These people are sick," he added.

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

Polls suggest Mr Trump has fallen further behind Ms Clinton nationally and in most battleground states.

Early in-person voting is underway in 20 states, including Ohio, where President Barack Obama railed against Trump a day after first lady Michelle Obama declared in a passionate speech, "Enough is enough."

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The Obamas both seized on Mr Trump's words, captured in a video released last week, bragging about kissing and groping women. The 70-year-old billionaire has apologised, but also repeatedly dismissed his comments as "locker room talk."