Six men have sexually assaulted a woman and punched another in the face in Melbourne’s CBD during a spate of robberies overnight.

The women had been on Queen Street before 4am on Saturday when six men stole their portable audio speaker and tobacco, before attacking the pair, Victoria Police say.

The offenders, including a teenager of African-appearance wearing a Balenciaga T-shirt, fled after the attack, Victoria Police said in a statement released last night.

But that wasn’t the start of the gang’s escapades.

Five men approached a stranger on Swanston Street about 8.45pm on Friday and unsuccessfully tried to steal his phone and wallet, before running away.

The offenders tried their luck a second time, stealing tobacco and attempting to take a mobile phone from two people on Banana Alley after midnight on Saturday.

The group fled, with the victims chasing the offenders before being assaulted.

The pursuers were taken to hospital with non-life-threatening injuries.

At least two of the offenders may have been involved in a fourth robbery outside a Southbank restaurant about 7am on Saturday when two people had their phones stolen.

One of the victims was headbutted and suffered a minor injury.

Two men have been arrested and are assisting police with inquiries.