Man injured in Sydney 'explosion' and fire

A man has been seriously burned when a shop exploded and caught fire on Sydney's lower north shore.

Emergency services were called to reports of an explosion and fire on Waters Road in Neutral Bay after 5am on Sunday.

A 42-year-old man was found on the footpath with burns to his legs.

He was taken to Royal North Shore Hospital, where he remains in a critical but stable condition.

Residents were evacuated from a home above the shop and some were treated for smoke inhalation.

Investigators are working to determine the cause of the blaze and have called for witnesses to come forward.