US comic Bill Cosby has been charged with sexual assault in Pennsylvania over an incident that took place in 2004, a prosecutor said today -- the first criminal charges filed against the actor after dozens of women claimed abuse.

"Mr Cosby is charged with aggravated indecent assault. This is a felony of the first degree," Kevin Steele, assistant district attorney for the state's Montgomery County, told reporters in Norristown, in the suburbs of Philadelphia.

Cosby, 78, was to be arraigned on the charge of aggravated indecent assault later today.

The charges stems from allegations made by a former employee of Temple University in Philadelphia, who says Cosby assaulted her at his home near the East Coast city in 2004.

"On the evening in question, Mr Cosby urged her to take pills that he provided to her and to drink wine -- the effect of which rendered her unable to move, (or to) respond to his advances, and he committed aggravated indecent assault upon her," Steele said.

Steele said the charges stemmed from new evidence in the case that came to light in July, prompting the reopening of the investigation.

"A prosecutor's job is to follow the evidence wherever it leads and whenever it comes to light," Steele said.

Cosby has been a star standup comedian and celebrity television pitchman for decades, but attained his greatest fame for his role as the lovable family doctor and pater familias in the hit 1980s sitcom "The Cosby Show."



More than 50 women have already publicly claimed abuse by Cosby, but his attorneys have repeatedly denied any wrongdoing by the comedian, who has gone from megastar to pariah in the face of the allegations, which span four decades.