Emergency services scrambled to the Love Machine nightclub in Prahran, southeast of Melbourne, near Little Chapel Street and Malvern Road. The victims have been rushed to hospital for treatment and surgery. A 28-year-old and another unidentified man are in a critical condition and two others, one aged 29 and the other in his 50s are stable, Victoria Police have confirmed.
The gunman remains on the run following the drive-by shooting.
The Age reports a security guard was shot in the face, and another guard and a patron were wounded in the shooting involving a stolen black Porsche Cayenne.
People were urged to avoid to the area around the venue as police cordons remain in place.
No arrests have been made so far.
Victoria police have launched an official investigation into the attack.
People have been urged to avoid the area and that anyone with information or footage of the incident to contact Crime Stoppers on 1800 333 000.
Two of the victims are security guards, the Sydney Morning Herald reports.
Australia introduced strict gun laws after 35 people were killed in Tasmania in 1996.
Last year seven were killed in a murder-suicide in Western Australia.
The shooting comes just a month after the Christchurch massacre in New Zealand.
The terrorist attack killed 50 people including children at two mosques.
Prime Minister Jacinda Ardern described it as “one of New Zealand’s darkest days”.
A 28-year-old Australian man was arrested and charged with murder.