Roy Moore, a Republican nominee for US Senate in Alabama, has been accused of initiating a sexual encounter with a woman when she was just 14 years old.

Leigh Corfman claims Moore, who was a 32-year-old district attorney at the time, introduced himself to her and her mother outside a courtroom in Etowah County, Alabama, in 1979. Following that initial meeting and getting her phone number, Moore allegedly picked her up and drove her twice to his home in the woods.

There, Corfman alleges that Moore kissed her, removed his and her clothes and touched her over her bra and underwear. He also guided her hand to touch him over his underwear, Corfman told The Washington Post.

Corfman said the two did not have intercourse.

Moore is running in the special election for Attorney General Jeff Sessions' Senate seat against former US attorney Doug Jones, a Democrat. The election is set for 12 December.

At least three other women interviewed by The Post alleged that Moore pursued them when they were between the ages of 16 and 18 and he was in his early 30s. The women said they found the attention flattering at the time, but troubling once they grew older.

However, none of three women say that Moore forced them into a relationship or sexual contact.

Wendy Miller said she was 14 when Moore first approached her, but 16 when he asked her out on dates. Debbie Wesson Gibson told the Post she was 17 when she met Moore during her high school civics class and went on several dates that included kissing.

The third woman, Gloria Thacker Season, said she was 18 when she began dating Moore. Their dates reportedly included bottles of Mateus Rosé wine, despite the drinking age in Alabama being 19.

Several key Republicans, including Senate Majority Leader Mitch McConnell and Senator John McCain, are calling for Moore to step aside if the reports are true.

"If these allegations are true, he must step aside," McConnell (R-Ky) said.

Senator Cory Gardner (R-Colo), the chairman of the National Republican Senatorial Committee, called the allegations "deeply troubling" and called on Moore to drop out if they are found to be true.

McCain (R-Ariz), who called the allegations "deeply disturbing and disqualifying," said Moore should drop out immediately. "He should immediately step aside and allow the people of Alabama to elect a candidate they can be proud of," McCain said in a statement.

Moore, now 70, denied the allegations in a written statement to the Post. He said: "These allegations are completely false and are a desperate political attack by the National Democratic Party and the Washington Post on this campaign."

His campaign added that if the allegations were true, they would have emerged during Moore's previous campaigns. The campaign went on to say "this garbage is the very definition of fake news".