An accused rapist sexually assaulted a female ­officer at Rikers Island as he was being transported from his cell, sources said.

Dexter Bell, who was awaiting trial on rape and robbery raps, savagely assaulted the officer while being moved at the high-security Otis Bantum Correctional Center Sunday, law-enforcement sources said.

Bell is now charged with felony sex assault in the ­attack on the officer.

A spokeswoman for the Department of Correction said the officer was “able to quickly bring the situation under control” and the ­“inmate has been arrested in connection with this ­unacceptable incident.”

The officer, Samantha Moscoso, painted a more terrifying picture in an ­interview with WABC/Channel 7.

“He violated me,” she said. “I had to . . . get him off me by any means possible.”