The so-called Apex gang came to public attention after a large-scale brawl in Melbourne's city centre last year. Credit:twitter.com/@russmulry It is now believed a phone call made to Triple 0 was made by a Channel 7 reporter who had information that a melee was planned. Police said the reporter initially contacted the force's media unit and was directed to contact the emergency number. Mr Crisp said the information was not supported by any other police intelligence. "It wasn't verified, we didn't see any need to significantly increase our resources at that time," he said.

Apex gang members rioting outside Flinders Street station last March Credit:@russmulry, via Twitter Members of the Apex street gang, who are predominantly young people of South Sudanese and Islander descent, ran riot in Federation Square and along Swanston Street, where families were celebrating Melbourne's Moomba festival. The rolling brawl sent terrified bystanders running for cover and forced others to hide inside restaurants. Rival teenage street gangs brawled in Melbourne CBD marring Moomba celebrations. It is believed the gang, linked to recent violent car thefts and threats of violence, later clashed with rival gang Islander 23, who are mainly of Polynesian descent.

Mr Crisp said officers on the ground told him two street gangs were not fighting each other, rather, it was one large group of mainly young men trying to provoke bystanders and police. Police out in force on Sunday night, after Saturday's riot. Credit:Chris Hopkins "That's not to say there wasn't some sort of skirmish between different young men, but it wasn't one group against the other," Mr Crisp said. But police have harboured specific concerns about South Sudanese youths for some time. The fight was reportedly planned via social media app Snapchat. Credit:Courtesy of Seven News

Just weeks before the riot, senior officers met with community leaders and representatives of the Andrews Government. On Monday, force command held a high-level meeting to address how to secure major events in the future. There have been similar, albeit to a much lesser scale, styles of attack at other CBD events including White Night and New Years Eve. Police sources said every available member from the Operational Response Unit was called to control the unfolding situation on Saturday, but crews of officers were unavailable after being sent to a music festival in Charlton and to help with a operation targeting the road toll. Mr Crisp would not discuss the number of police who attended initially and were subsequently called-in, citing security reasons. He said officers exercised "great restraint" in the face of extreme provocation, which included getting "up in" officers' faces and filming "whatever" members were saying to them.

Only four rioters were arrested - two for drunkenness, one for carrying a stun gun, and another for allegedly knocking an officer's radio or phone into their face. Mr Crisp said more were expected given the "clear footage" they have of them from CCTV cameras. A bystander who admitted himself to The Alfred hospital after suffering a head injury on the corner of Flinders Lane and Swanston has since been discharged.

Police first used capsicum spray to disperse the crowd at Federation Square about 8pm as onlookers fled for cover. "We were absolutely terrified," said Troy West, from Bendigo, who spent 45 minutes locked inside a Federation Square restaurant as police tried to contain the wild group outside. The group then ran to City Square and threw metal chairs from outdoor cafes. One nearby retail worker saw scores of people arguing. Some were hitting and pulling at each other, she said. "The whole street was blocked by those people," she said.

Plaza Ballroom chef Rachael Honeycomb said she left work at 11pm and saw men yelling into a megaphone. Everyone was confused. "I think a lot of people were trying to figure out what was going on," she said. Mr Crisp said the big question of why these young people rioted remained unanswered. "How did they get to be in this position in the first place and where have they been failed in the system along the way?" he told 3AW.

Mr Crisp told Fairfax Media senior members in multi-cultural communities in the south-east expressed their frustrations to him on Monday. "There is extreme frustration in the children, the young boys, that they aren't listening to their parents, they're not listening to the community and they're engaging in this behaviour that is criminal," he said. "These young people would have known what they were doing was wrong, it matters not what their cultural background is." The issue of gang violence involving South Sudanese teenagers was discussed at two meetings on February 19 and a week later on February 26. "Victoria Police has recently been engaging with senior members of the South Sudanese community, including the leadership of the South Sudanese Community Association in Victoria. A range of issues have been raised," the meeting invite stated.

Both meetings were staged at the Victoria Police Centre on Flinders Street. Chief Commissioner Graham Ashton also announced an increase in resources for Operation Tense, a taskforce set up in November last year to monitor and crack down on the Apex gang. The taskforce has so far arrested 33 gang members. "Of those 33, we've had 20 who have been remanded in custody in relation to aggravated burglaries, robberies, assaults and theft of and theft from motor cars," he said. Mr Ashton revealed the Apex gang had attended New Year's Eve and last month's White Night celebrations in the CBD.

On Sunday night, Victoria Police circulated an email to members warning them against talking about the nationalities of offenders. The email stated it was a "multi-cultural" incident and officers had to ensure they do not target specific groups. Police said they handled the situation appropriately, but were concerned about fresh threats on social media. Mr Ashton said at least 100 officers would continue to patrol the CBD around the Moomba festival in light of more promises of violence on Sunday night, which did not eventuate. With Allison Worrall and Steve Lillebuen