A 13-year-old girl has been shot in the thigh in what police believe was a targeted attack in Sydney's west on Tuesday night.

Emergency services were called to a home in Guildford following reports shots had been fired at an open garage where a group of young girls were sitting and talking.

Neighbours reported hearing "five or six pops" and quickly spilled onto Constance Street, where the incident happened about 9:45pm.

Superintendent Matt Appleton of the Cumberland Police Area Command said a silver SUV was seen pulling up near the driveway at the premises at the time.

The girl was taken to the Children's Hospital Westmead in a serious but stable condition.

Superintendent Appleton called the incident "an atrocious crime" and said "anyone [who] would fire into any premises … [and] for a young girl 13-year-old girl to be wounded is just shocking."

The young girl did not reside at the home but was visiting.

Police said they believe shots were fired from the passenger side of an SUV, meaning at least two people could have been in the car.

The direction in which the SUV headed is unknown.

A woman argues with police near where a young girl was shot in Guildford. ( ABC News )

Several people engaged in heated discussions with officers, with some waving their hands while others wiped back tears.

A woman named Dianne, who said she heard several bangs, said: "I got scared, it sounded like fireworks."

"I saw police cars everywhere. They blocked the street off."

At one stage, several men ducked under police tape that was blocking the area, and had to be pushed back.

Another woman who heard the incident unfold said it was not the first time there had been drama in the area.

"We were sitting at home watching television and all of a sudden we heard five or six pops," she said.

"I said to my husband that didn't sound like a car backfiring, that sounded like gunshots.

"Then we heard the police coming, and we heard a bit of screaming.

"It's the sort of area where it happens all the time, it was just another night in Guildford."