An Ottawa man is facing charges after allegedly sexually assaulting a woman with the developmental capacity of an eight-year-old, police say.

It happened late Monday afternoon on Riverside Drive at Bank Street, not far from the Billings Bridge Shopping Centre, Ottawa police said in a news release issued Wednesday.

The woman, who is in her 20s, was approached by a man as she was waiting for the bus. He then sexually assaulted her in a nearby washroom, took her phone and sexually assaulted her again, police allege.

"After a brief conversation, they walked to a nearby store and the man sexually assaulted the woman in the washroom. He took her cellphone from her when she tried to call for help. The [man] sexually assaulted her a second time before she was able to call for assistance," the news release stated.

A 22-year-old man was later charged with two counts of sexual assault and one count of mischief.

He was scheduled to appear in court Wednesday.