A 12-year-old boy has died in a house fire in Adelaide's inner south.

A 12-year-old boy has died in a house fire in Adelaide and his father is in a critical condition after trying to rescue his son.

The boy was found dead inside the home early on Monday morning and his 65-year-old father was taken to the Royal Adelaide Hospital suffering extensive burns.

Fire crews were called to the property – a single storey home with a separate accommodation building at the rear – on Smith-Dorrien Street in suburban Netherby just before 3.30am and were told there were still people inside.

Six international students living in the rear building managed to escape unhurt, while two people were pulled from the house itself.

It took 35 firefighters half an hour to bring the blaze under control. The home suffered extensive damage with part of the roof collapsing.

The damage bill was put at $250,000 for the house and $5000 for the rear building.

Fire crews were hampered by limited access due to low-hanging powerlines and were still monitoring hotspots as investigations continued.

Police and fire authorities used drones as part of their investigation into the cause of the blaze which could take several days to determine.