Left-wing extremist group Antifa has been condemned for posting a vile Facebook post praising a man who killed at least 59 people in Las Vegas in the worst mass shooting in American history.

Screenshots of the Melbourne chapter's deleted social media post have been reposted on to their site, highlighting their support for dead 64-year-old gunman Stephen Paddock.

'One of our comrades from our Las Vegas branch has made these fascist Trump supporting dogs pay,' it said on Tuesday morning.

Left-wing extremist group Melbourne Antifa's vile Facebook post praising Las Vegas shooter

Antifa's Melbourne arm praised Stephen Paddock for making 'Trump supporting fascists pay'

Melbourne Antifa's post was published little more than 12 hours after the carnage across the road from the Mandalay Bay Resort, as Jason Aldean performed on stage to close out the third and final day of the Route 91 Harvest Music Festival.

Paddock, a millionaire accountant who lived a 90-minute drive away from Las Vegas in the city of Mesquite, Nevada, in a retirement village, opened fire on a festival which 22,000 people were attending.

The offensive social media message praising him was widely condemned as screen shots of it were re-posted on Melbourne Antifa's Facebook page.

'You would have to be the biggest f***wit ever,' one man wrote.

Another woman wrote: 'You filthy piece of rats***.'

Several people used expletives to express their anger at Melbourne Antifa for praising gunman

Melbourne Antifa temporarily posted a vile message after the carnage at a Las Vegas festival

One man referred to Melbourne Antifa as 'commie scum' for their vile Facebook post

Melbourne Antifa is part of a global movement of so-called anti-fascists.

In June, they took responsibility for ambushing Sky News presenter and conservative columnist Andrew Bolt with a glitter bomb outside a Melbourne book launch, before he fended them off and made them run during the encounter captured on video.

Now they are praising a shooting that has killed at least 59 people and injured another 527 at a country music festival across the road from the Mandalay Bay Resort.

One man said: 'Shame on you, commie scum.'

While ISIS claimed responsibility for the attack, the FBI says the shooter had no connection with the terrorist group.