A woman in her 20s was rushed to hospital in critical condition after a hit and run on Preston Street Monday afternoon, Ottawa paramedics said.

The collision happened at the corner of Preston and Pamilla streets around 2:20 p.m.

Paramedics said the woman suffered a "life-threatening head injury" and that she was unconscious when she was rushed to the trauma centre. 

Police are asking for the public's help in locating a vehicle involved in the collision. They are looking for a grey, four-door Honda Civic with a missing passenger headlight and damage to the front lower bumper. The front passenger windshield might also be damaged, police said.

Anyone with information about the vehicle's whereabouts is asked to call 911. 

Ottawa police closed a section of Preston Street while they investigated the collision, but it has since reopened to motorists.