Image copyright AFP/Getty Image caption Joe Biden served as Barack Obama's vice president for eight years

Former US Vice-President Joe Biden has denied allegations of misconduct ahead of his widely expected announcement of a presidential run.

Lucy Flores, a former Nevada Assembly member, says Mr Biden kissed her on the back of her head at a campaign event.

A second woman, Amy Lappos, said Mr Biden had acted inappropriately by touching her face with both hands and rubbing noses with her a decade ago.

Mr Biden, 76, served as Barack Obama's vice-president for eight years.

The former Delaware senator is seen as a possible frontrunner in the race for the Democratic presidential nomination even though he has not announced his candidacy.

What are the allegations?

The allegations first appeared on Friday in an article Ms Flores wrote for The Cut magazine.

Ms Flores was running as the Democratic candidate for Nevada's lieutenant governor in 2014 when the then-vice president flew in to support her bid.

As she prepared to go on stage, Ms Flores say Mr Biden placed two hands on her shoulders from behind.

"I felt him get closer to me from behind. He leaned further in and inhaled my hair. I was mortified," she wrote. "He proceeded to plant a big slow kiss on the back of my head. My brain couldn't process what was happening."

Image copyright Getty Images Image caption Lucy Flores alleges Mr Biden kissed her on the back of the head ahead of a 2014 campaign event

She wrote: "I had never experienced anything so blatantly inappropriate."

On Monday, a second allegation surfaced.

Amy Lappos, a former aide to Democratic congressman Jim Hines of Connecticut, said Mr Biden touched her inappropriately at a fundraiser in a private home in Hartford, Connecticut, in October 2009.

She told the Hartford Courant that the then-vice-president entered the kitchen to thank the group of aides, before wrapping both hands around Ms Lappos' face and pulling her in to rub noses with her.

Ms Lappos, now 43, said in a statement to US media: "Uninvited affection is not okay. Objectifying women is not okay.

"Men who invade a woman's personal space, touch women inappropriately, sexually harass women and feed rape culture have no place in a position of power.

"Referring to this type of behaviour as 'simply affection' or 'grandpa-like' or 'friendly' is ridiculously dismissive and part of the problem."

She called on Mr Biden not to run for the White House and to clear the way for one of the many female candidates.

How did Mr Biden respond?

Mr Biden's spokesman Bill Russo initially said neither the vice-president nor his staff had any idea that "Ms Flores had been at any time uncomfortable, nor do they recall what she describes".

But on Sunday Mr Biden issued a statement himself, and promised to "pay attention" to Ms Flores - while reiterating he did not remember the incident.

"In my many years on the campaign trail and in public life, I have offered countless handshakes, hugs, expressions of affection, support and comfort. And not once - never - did I believe I acted inappropriately," it read.

"But we have arrived at an important time when women feel they can and should relate their experiences, and men should pay attention. And I will," he added.

Speaking in a CNN interview on Sunday, Ms Flores said Mr Biden's statement was "certainly better" than his spokesman's initial response, but called his behaviour "completely inappropriate" and something to think about of a person "who is considering running for president".

On Monday, Biden aides began to push back more aggressively against some of the criticism.

In a statement, his spokesman Bill Russo accused "right wing trolls" from "the dark recesses of the internet" of presenting harmless images of Mr Biden interacting with women as evidence of inappropriate touching.

What's been the reaction?

A number of candidates for the 2020 Democratic presidential nomination have backed Ms Flores.

"I think what this speaks to is the need to fundamentally change the culture of this country," Senator Bernie Sanders told Face the Nation on CBS, saying he had no reason not to believe Ms Flores.

She previously campaigned for Mr Sanders in his 2016 nomination run.

Senator Elizabeth Warren said Mr Biden "needs to give an answer", and Senator Amy Klobuchar said that in politics "people raise issues and they have to address them".

Image copyright Getty Images Image caption Lucy Flores campaigned for Bernie Sanders in 2016

But many supporters have leapt to Mr Biden's defence.

Cynthia Hogan, a former aide to the vice-president, told the New York Times that Mr Biden "treated us with respect and insisted that others do the same".

And Stephanie Carter, the wife of former defence secretary Ashton Carter, defended her "close friend" in a blog post.

A photo of Mr Biden holding her shoulders during her husband's swearing-in ceremony drew questions at the time and afterwards.

But in a blog post, Ms Carter wrote that the vice-president "could sense I was uncharacteristically nervous" at the event "and quickly gave me a hug", she wrote.

"But a still shot taken from a video... came to be the lasting image of that day."