Actresses Natasha Henstridge and Olivia Munn and four other women have accused Ratner, director of "Rush Hour" and "X-Men: The Last Stand," of sexual misconduct, the Los Angeles Times reported.
Meanwhile NPR emailed staff to tell them Oreskes, senior vice president for news, had been axed following allegations of sexual harassment from women dating back to the 1990s.
Ratner, 48, a prolific director and producer whose movies have grossed more than $2 billion worldwide, strongly rejected the allegations in a statement to the newspaper from his attorney.
"He strong-armed me in a real way. He physically forced himself on me," said Henstridge, who has appeared in the movies "Species" and "The Whole Nine Yards."
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"At some point, I gave in and he did his thing," she told the newspaper.
Henstridge said she was inspired to come forward by the stories of other women who have reported sexual misconduct by powerful Miramax producer Harvey Weinstein and director James Toback.
Munn recounted the incident in a book she wrote but did not then name the director involved.
She said the time had come to speak up.
"I've made specific, conscientious choices not to work with Brett Ratner," Munn told the newspaper.
Four other women also recounted stories to the newspaper about Ratner being sexually inappropriate or intimidating.
Ratner, through his attorney, Martin Singer, rejected the accounts.
"Furthermore, no woman has ever requested or received any financial settlement from my client," Singer said.
The Beverly Hills Police Department said yesterday they were investigating "multiple complaints" against Weinstein and Toback, who face numerous allegations of unwanted sexual encounters but deny forcing themselves on women.
Accounts of abuse by Weinstein that were published last month in The New York Times and The New Yorker encouraged others to speak out, unleashing a cascade of allegations of sexual harassment and assault against leading figures in Hollywood and elsewhere.
The LA Times interviewed 38 women who accused Toback of unwanted sexual encounters, and the paper said it was inundated with emails and phone calls from more than 200 additional women after the publication of its story.
NPR CEO Jarl Mohn wrote in an email seen by AFP to NPR staff today that he had asked Oreskes for his resignation because of "inappropriate behavior" and the news executive had obliged.
"I am deeply sorry to the people I hurt. My behavior was wrong and inexcusable, and I accept full responsibility," Oreskes was quoted by the station as saying in a statement.
He also has been accused of harassment by an employee at NPR, the station reported on its website.
"When anyone, but particularly someone in power, violates a policy, acts in ways that are inappropriate, or takes steps that do not contribute to building a positive workplace, it breaks a trust," Mohn wrote.
"That trust is about looking out for each other, doing the right thing, and acting as one team. It is sacred to me. I am committed to rebuilding trust, and my leadership team is as well.