An Australian woman has been shot dead by police in the US after calling 911 for help.

The shooting of an Australian woman by US police has raised serious concerns after it was revealed the officers didn’t have their body cameras turned on.

Justine Damond, believed to be aged in her 40s, was killed in Minneapolis about 11.30pm local time on Saturday after two officers responded to a report of a possible assault.

Ms Damond, originally from Sydney and also known as Justine Ruszczyk, was a trained veterinarian who worked as a spiritual healer and meditation teacher.

Her stepson Zach Damond, 22, said she called police after hearing a noise near their house in the suburb of Fulton.

"My mum was shot for reasons I don't know," Mr Damond said in a video posted on Facebook.

"I demand answers ... I'm so done with all this violence.

"I just know she heard a sound in the alley so then she called the police and the cops showed up.

"She was a very passionate woman, she probably thought something bad was happening and then next thing I know they take my best friend's life."

Ms Damond ran her meditation workshops at the Lake Harriet Spiritual Community, which paid tribute in a Facebook post.

"We are so sad to report the tragic shooting of Justine Damond," the community's post said.

"Justine was one of the most loving people you would ever meet. We can't even imagine LHSC without her."

Ms Damond, whose partner is Don Damond, 50, is believed to have been living in the US for at least the past three years.

Update: Woman fatally shot by Mpls. police was native Australian, 'the most loving woman,' engaged to Mpls. man https://t.co/wtpVuMnDyL pic.twitter.com/SCrZV0uQ2R

— Star Tribune (@StarTribune) July 16, 2017

Minneapolis mayor Betsy Hodges wants to know why the officers' body cameras were off.

"I am heartsick and deeply disturbed by what happened," she posted on Facebook.

"I have been working on behalf of all of you all night and all day and I will continue to do so.

"I share your questions and concerns and continue to seek answers."

The Minnesota Bureau of Criminal Apprehension said two Minneapolis police officers responded to a 911 call of a possible assault just north of the 5100 block of Washburn Avenue South.

"At one point an officer fired their weapon, fatally striking a woman," it said in a statement.

"The officers' body cameras were not turned on at the time and the squad camera did not capture the incident.

"Investigators are attempting to determine whether any video of the incident exists."

Ms Damond's personal website says she trained as a veterinarian and practised yoga and meditation for 17 years.

The Department of Foreign Affairs and Trade says it's providing consular support to the family of an Australian woman killed in the US.

A vigil for Ms Damond is planned for 6pm Sunday in Fulton, near the scene of the shooting.

"Investigators are attempting to determine whether any video of the incident exists."