Man's body found after Sydney house fire

A man has died in a townhouse fire in Sydney's west.

Firefighters were called to the blaze on O'Brien St at Mount Druitt just after 1am on Wednesday.

When they arrived, one person had fled the burning home but a man was missing and his body was later found inside the extensively damaged townhouse, NSW Fire and Rescue said.

Police have set up a crime scene and the cause of the fire is still unknown.