Melbourne: Two people are fighting for their lives after a shooting outside a Melbourne nightclub, police said Sunday, amid a spate of gun violence in Australia's second-largest city.

Police said four men were taken to hospital -- two in a critical condition -- after "multiple people were shot" outside the venue in the trendy inner-city suburb of Prahran early Sunday morning.

Three of the men were aged between 29 and 50, with the age of the fourth yet to be determined, police said.

A police spokeswoman said the shooting was not believed to be linked to terrorism. Investigators were probing links to motorcycle gangs, The Age newspaper in Melbourne reported.

The latest incident came after a spate of shootings in Melbourne in March that left five people dead in four separate incidents. Two of the incidents were believed to be gang-related.

Mass shootings are rare in Australia, which has strict firearms laws introduced in 1996 after 35 people were killed by a gunman in Port Arthur.

A murder-suicide last year which left seven members of a family dead in Western Australia was the country's worst mass shooting since the Port Arthur attack.