A mother saved her kids from a fire by throwing them out the window.

A mother threw her toddler and two-day-old baby from a second story window into the arms of a neighbour to save them from an apartment fire.

The fire started in the Sydney apartment block around 9.30pm yesterday while the 27-year-old woman was cooking, and quickly engulfed the apartment.

As the wall of flame moved towards her, blocking her from the front door, she moved with her toddler and two-day-old baby towards the window.

A neighbour, who had dragged a mattress from his own apartment stood below to catch them.

“I was watching the football. I see the smoke come out of the house. I have to help you know,” he told 9NEWS.

The children were uninjured and their mother was rescued by fire fighters soon after and treated for smoke inhalation and cuts to her feet.

A total of 50 residents has to be evacuated from the Lakemba apartment block, a 19-year-old woman and 65-year-old man were then treated for smoke inhalation.