Inside the Sydney backpacker hostel gutted by fire

A backpacker hostel in Sydney's inner-west has been left charred after fire forced the evacuation of 28 people overnight.

The building, on Parramatta Road in Concord, suffered extensive damage on the bottom level and smoke damage on all three levels.

The blaze started in a room on the bottom floor after a bunk bed caught fire. The flames spread from room to room as a resident attempted to extinguish the fire with his hands.

The blaze has been described as "very scary" with the thick black smoke making it difficult for residents to escape the unit block.

Two men were unable to flee and were rescued by fire fighters using ladders from the top floor.

Fire investigators are looking into whether a lit cigarette was left unattended in the room.

One man was taken to hospital with burns to his hands while a woman was treated for smoke inhalation.