WA Police Minister Paul Papalia has said pedestrians are responsible for their own safety in the wake of a young Indigenous woman being left fighting for her life after she was struck down by a police car in Perth.

Colleen Calgaret, 20, suffered serious head injuries after being struck by the vehicle in Northbridge.

WA Police confirmed a marked police car hit Ms Calgaret on Wellington Street around 1:15 am on Saturday.

She was taken to hospital as a result of her injuries and the incident is under investigation by the Major Crash division of WA Police.

Nine News reports Ms Calgaret's partner and baby son are by her side in intensive care in Royal Perth Hospital.

Her sister Mariah Calgaret told local media the family has been left "in limbo".

"We don't even know ourselves, from the moment we found out, what exactly happened," she said.

"If anyone has footage we would like to see it ourselves."

It has been reported that WA Police will not say whether the vehicle was turning left on to Wellington Street from the Horseshoe Bridge, which is illegal, or if the officer driving the vehicle was responding to an incident at the time.

Colleen Calgaret's sister Jasmine Calgaret said the family needed answers.

"I think we should have been told more about the situation and what is going on in the investigation," she said.

Minister Papalia told a press conference on Sunday that ultimately pedestrians are responsible for their own safety.

Asked if he could speak about the incident, the Minister said "not too much; obviously this is being investigated... any crash involving police is investigated thoroughly".

Mr Papalia said he was reticient to comment but was not aware of any police wrongdoing.

"It is a terrible thing to have happened... The woman is being cared for in hospital and her family is being fully informed.

"There has been a couple of terrible incidents, tragically one woman died after being hit by a vehicle (in a separate incident on the weekend).

"But you have got to remember ultimately as a pedestrian you are the one responsible for your own safety... If you are crossing the road you have got to watch out because vehicles are much bigger and faster than you."

According to Western Australia's road rules, drivers are required by law to give way to pedestrians crossing the road the vehicle is turning into.

WA Police and Major Crash investigators are seeking anyone who witnessed the crash or who has footage from a dash-cam to come forward and contact Crime Stoppers on 1800 333 000.