'Absolutely false,' Trump says after sexual assault allegations

With his numbers dropping in opinion polls ahead of the Nov. 8 election, the Republican U.S. presidential nominee told supporters at a rally in Florida that his campaign was engaged in "a struggle for the survival of our nation."

Trump said accusations that he groped women in a series of incidents going back to the 1980s were part of a coordinated attempt to keep him from the Oval Office.

"These vicious claims about me of inappropriate conduct with women are totally and absolutely false," he said, adding that "the Clintons know it." He said he would make public at some point evidence to dispute the charges.

"I've never met these people. I don't even know who they are. They're made-up stories," Trump said later on Thursday during a speech in Ohio.

Trump spoke after The New York Times reported that two women said they had endured sexual aggression from him, and several other women made similar allegations in other media outlets.

The New York businessman's campaign was already struggling to contain a crisis after a video surfaced last week showing him bragging in 2005 about groping women and making unwanted sexual advances.

First lady Michelle Obama criticized Trump in scathing terms in a campaign speech for Clinton in New Hampshire on Thursday.

Her voice close to cracking with emotion, Obama said, "This was a powerful individual speaking freely and openly about sexually predatory behavior, and actually bragging about kissing and groping women, using language so obscene that many of us were worried about our children hearing it when we turn on the TV."

"It's one of countless examples of how he has treated women his whole life," she added. "... The shameful comments about our bodies, the disrespect of our ambitions and intellect, the belief that you can do anything you want to a woman -- it is cruel."

One woman, Jessica Leeds, appeared on camera on The New York Times website to recount how Trump grabbed her breasts and tried to put his hand up her skirt on a flight from the Midwest to New York in or around 1980.

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Leeds told CNN on Thursday that Trump also kissed her face in an incident that lasted about 15 minutes. "That's long enough," she said.

The second woman, Rachel Crooks, described how Trump "kissed me directly on the mouth" in an unwanted advance in 2005 at Trump Tower in Manhattan, where she was a receptionist at a real estate firm.

Reuters could not independently verify the incidents. Leeds and Crooks did not respond to requests for comment from Reuters.

The New York Times said on Thursday it stood by its story and rejected charges the article was libelous after a lawyer for Trump threatened legal action and demanded a retraction.