Man fighting for life after tobacco shop firebombing

A man is fighting for his life in hospital after being found with severe burns following a tobacco shop firebombing.

The person, who is yet to be identified, was discovered near The Boss tobacco store in Melton, on the outskirts of Melbourne's northwest, about 3am on Thursday.

Fire crews found the man after responding to the fire, which fully involved the stop.

There were no occupants in the building when fire crews arrived, Fire Rescue Victoria confirmed.

Crews donned breathing apparatus and began attacking the fire as it threatened to spread to neighbouring stores, which share a roof space.

Detectives remained at the scene on Thursday, with sections of Melton's High Street sectioned off.

"The exact circumstances surrounding the incident are being investigated," a police spokesperson said.