US police shoot Australian woman who called for help

An Australian woman who called 911 to report a crime has allegedly been shot dead by police in the US city of Minneapolis.

Justine Damond, a 40-year-old Australian woman living in Minneapolis, called police on Saturday night, according to the Star Tribune.

An investigation into the incident is underway, but could be difficult as the officers' body cameras were reportedly not switched on, and a camera in a squad car did not capture it.

Friends told the Star Tribune Ms Damond, a veterinarian and meditation teacher, was planning to marry her fiancé in August.

"Basically my mum was shot for reasons I don't know," her stepson Zac said in a video posted to Facebook.

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

Minneapolis Mayor Betsy Hodges called the incident "tragic".

"I am heartsick and deeply disturbed by what occurred last night," she said in a statement.

"There are still many questions about what took place."

The Australian Department of Foriegn Affairs and Trade is providing consular assistance.