OKLAHOMA CITY — Oklahoma City's police chief has fired an officer accused of sexually assaulting 13 women while on duty.

The department said Daniel Holtzclaw was fired Thursday. Holtzclaw has pleaded not guilty to 36 charges.

Chief William Citty called the charges against Holtzclaw the "greatest abuse of police authority" in his 37 years on the force.

Holtzclaw's next court hearing is set for Jan. 21. A judge in November ordered Holtzclaw to face a trial and let him remain free on $609,000 bail.

The charges against the former officer include first-degree rape, sexual battery, forcible oral sodomy and indecent exposure.

Police began investigating Holtzclaw in June after a woman complained. Police spokesman Paco Balderrama told The Oklahoman newspaper (http://bit.ly/1wzHWdH ) the agency does a good job of policing itself.