The moment a jewellery thief wielding a syringe executed a smash and grab on a $100,000 watch has been caught on camera.

The wigged man who pulled off the brazen heist in Collins Street on Wednesday morning last week remains on the run.

Click PLAY to watch it unfold

The man threatened staff with a syringe and smashed a glass display before stealing the watch.

The offender was wearing black rubber gloves and fled the area on a bicycle.

The man also has a distinctive tattoo on his left bicep.

Police have released CCTV and images of a man they believe may be able to assist with their investigation.

Click PLAY to hear Ross and John discuss the matter with Victoria Police