07/10/2017 7:28 AM AEDT | Updated 07/10/2017 7:28 AM AEDT

Man Fighting For Life After Suffering Horrific Burns In Sydney House Fire

The victim is critical in hospital.

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Police have set up a crime scene in Gymea.

A man is clinging to life in hospital after being seriously burnt in a house fire in Sydney's south.

The man was burnt when the fire broke out at a granny flat at Gymea about 1.30am Sunday, police said.

The 39-year-old victim was taken to Royal North Shore Hospital in a critical condition, suffering extensive burns to his body.

Local police have established a crime scene.

The cause of the fire has not yet been determined and police are investigating.