A heavy police presence in the centre of Melbourne is keeping a lid on threats of violence from a gang who vowed to return to a community festival for a second night of unruliness.
The Apex gang, which has around 100 members, some as young as 12, terrorised the public and taunted police during Moomba celebrations on Saturday night.
They threatened on social media to return and run amok again on Sunday night.
As a result there are 100 Victoria Police officers patrolling the city.
"We haven't been told of any incidents," a police spokeswoman told AAP about 9.30pm.
Some youths were questioned by police as they exited Flinders Street train station, but many Moomba attendees were unaffected by additional uniformed police presence.
Earlier on Sunday, Chief Commissioner Graham Ashton warned gang members they'd be facing a tougher response compared to Saturday night.
"We acted really responsibly (on Saturday night) and we'll act responsibly tonight - but we'll do so in greater number and with less tolerance for the sort of behaviour we saw last night," Mr Ashton told reporters on Sunday.
Deputy Commissioner Andrew Crisp said police would make sure there were no further incidents.
"My clear message to those who are in any way thinking of engaging in stupid and violent behaviour is - stay away from the city," he said.
Mr Crisp also said reports that two separate street gangs were involved in Saturday's events were wrong.
Rather, it was just one large group involved in the violence, and the deputy commissioner pulled no punches when describing the chaos seen on Saturday.
"I'll even call it a riot - from my perspective it was riotous behaviour by this particular group," he said.
A man armed with a Taser was involved in Saturday night's riot which centred on Federation Square and surrounding areas.
Two young men were arrested for being drunk, another was arrested for assaulting an officer, and a fourth was arrested after allegedly being found with the Taser.
An innocent bystander - a young man - was taken to hospital with serious but not life-threatening injuries.
Apex is primarily based in Melbourne's southern suburbs, but members have previously ventured into the city centre looking to make trouble on New Year's Eve and for White Night, police say.
