A 27-year-old man has been arrested for allegedly sexually assaulting a woman in Sandy Hill after two passersby helped stop the attack.

The woman screamed for help when she was attacked from behind on Wilbrod Street near Nelson Street around 2 a.m. on Friday, according to Ottawa police.

Two men passing by in a vehicle stopped, chased the suspect and held him until police arrived.

The suspect was expected to appear in court Friday.

Ottawa police are asking anyone with information about this incident to contact the sexual assault unit at 613-236-1222, ext. 5944 or Crime Stoppers at 1-800-222-8477.