Australian police believe the father of three children who died in a Sydney house fire on Sunday is responsible for the tragedy.

Four children and their mother survived, but three died - including a 10-month-old.

The blaze at Lalor Park is being investigated as domestic violence.

Australian correspondent Oliver Peterson says police still need to follow correct processes.

"It is being alleged that the father was holding the door shut, saying - I want to die here. It is going to be alleged, once they can talk to this bloke - who's in a coma - that he set the house on fire and was trying to kill his family."

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