Five people injured and hundreds evacuated from Melbourne housing commission blaze

A man is in a critical condition with serious burns to his face after a Melbourne apartment block fire led to the evacuation of 300 people.

The man was burned on his face, arms and back and paramedics transported him to The Alfred hospital, paramedics say.

The fire brigade suspects a mattress was set alight in a corridor on the sixth floor of a housing commission tower on Napier Street in Fitzroy about 5am on Wednesday.

"Whilst the mattress was extinguished quickly, thick smoke filled the floors with some occupants unable to evacuate," fire service controller Heather Stockton said in a statement.

The fire was deemed suspicious and police were investigating.

Four other people, including a firefighter with smoke inhalation, were taken to hospital in stable conditions.

Paramedics assessed about 50 other people but none needed treatment.

Residents on the fifth, sixth and seven floors were evacuated and taken to the nearby Fitzroy Town Hall.