Two Sydney homes in neighbouring suburbs were sprayed with bullets and cars were set alight within minutes of each other, prompting a major police investigation.

Emergency services were first called to Wendy Close in Cabramatta around 12.45am on Thursday, where a house came under fire before a car parked outside was torched.

Just 15 minutes later, reports of loud bangs - believed to be gunfire - came from North Liverpool Road in Green Valley, roughly 10 kilometres away.

At the Cabramatta address, four people were inside the home when five gunshots were fired. The bullets hit the front of the house.

A white Toyota station wagon was then set on fire, with flames spreading to the front porch before firefighters managed to contain the blaze.

A 57-year-old woman was treated at the scene fo

See Full Page