A man has died moments after his arrest

A VICTORIAN man died shortly after he was arrested on Friday evening, prompting an urgent investigation into the mysterious circumstances surrounding the incident.

Police were called to an area of the Great Ocean Road, in Bellbrae, 100km southwest of Melbourne, about 7.30pm.

The officers had received reports that a man was "behaving erratically" near Hurst Road.

A police statement claimed the man was "arrested and then fell unconscious", but little detail is given about his condition or potential injuries.

"Emergency personnel (sic) attempted to revive him but were unsuccessful," the statement said.

Detectives from the Homicide Squad are now investigating the death in custody, while a post mortem examination of the man's body is being carried out.

The statement claimed that "all deaths in police custody are investigated by the Homicide Squad".

The matter will be overseen by officers from the Professional Standards Command.