Rowdy soccer fans in Melbourne let off more than four flares, with heavy orange smoke flooding a stadium at the clash between Melbourne Victory and Western Sydney Wanderers.
Fans at the game took to Twitter to express their concern after hearing at least five explosions at AAMI Stadium about 9.30pm (AEDT).
Kacey Lam tweeted a photo of the thick orange smoke, saying: "SIX LOUD BANGS. Anyone would think terrorists have overtaken AAMI."
Another fan, Alex Loft, tweeted: "kids and parents were walking out scared".
Earlier, soccer fans set off flares, broke chairs and glasses and threw sticks in a brawl outside the Royal Melbourne Hotel on Bourke Street just after 3.30pm (AEDT) on Saturday.
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At least four people were injured in the scuffle, police said.
Police spokeswoman Belinda Batty said no arrests were made and no assaults had been reported.
A man in his early 20s was taken to the Royal Melbourne Hospital with an upper-body injury, Ambulance Victoria confirmed.
He remains in a stable condition.
Two other patients were assessed at the scene by ambulance crews.
Police continue to investigate the incident and will review CCTV footage.
