Fire engulfs three southwest Sydney homes

Jamie McKinnell and Rachel Gray

Two homes have been destroyed and one severely damaged by a ferocious fire in southwest Sydney.

The blaze reportedly started in the backyard of one home on Napier Avenue in Lurnea about 12.30pm on Wednesday, before spreading to the homes on either side.

No one was in any of the three properties, with six crews racing to the scene to extinguish the blaze, a NSW Fire & Rescue spokesman told AAP.

"The first house was fully engulfed due to the ferocity of the fire," he said.

Neighbour Susan Coorey called emergency services after hearing explosions.

"It kept exploding and I'm saying 'please quickly come now', because it was spreading," she told reporters at the scene.

"It spread so fast."

One of the homes belonged to a family of five.

NSW Fire and Rescue spokesman Daniel Austin said it was a relief to hear nobody was inside the top level of one of the buildings.

"The flames were quite fierce and you could feel it back here on the street," he told reporters.