The new allegations came a day after Cosby was sued by a woman who said he molested her when she was a teenager in 1974.
Cosby has not been charged with any crimes.
More than a dozen women have accused the comedian of sexual abuse as far back as the 1960s as the allegations have scuttled Cosby’s television projects and led to cancellations of comedy performances, including two gigs in New York that were scheduled for Saturday.
The women, one who says she was 17 at the time of her encounter with Cosby, each sobbed while reading statements at a news conference organised by celebrity attorney Gloria Allred, who is known for her aggressive posture on women’s issues.
“For years, I did not tell anyone about what he had done to me because I was afraid,” said Beth Ferrier, who claims to have had an affair with Cosby in the mid-1980s. “I felt threatened by him, and I did not think anyone would believe me.”
Allred proposed the comedian should waive the statute of limitations that protects him from decades-old allegations or create a $100m fund to pay damages to accusers.
Cosby’s attorney has called allegations against Cosby discredited and defamatory.
A woman who gave her name only as Chelan said that as a 17-year-old in 1986, Cosby drugged her, gave her alcohol and began to fondle her before she blacked out.
Ferrier said she was one of the several “Jane Does” in a 2005 civil lawsuit that made similar accusations against Cosby and was later settled.
Another woman, Helen Hayes, accused Cosby of groping her breast at a restaurant in 1973.
Meanwhile, a lawsuit filed by Judy Huth, a California woman who accused Cosby of sexually battery when she was 15 at the Playboy Mansion in Los Angeles in 1974, is the first legal challenge to The Cosby Show star since the wave of allegations began last month.
Huth’s lawsuit uses a portion of California law that permits lawsuits up to three years after childhood sex abuse is “discovered” to have caused damages, no matter the plaintiff’s age, a hurdle legal experts say will be difficult to clear.