Seven “aggressive” young girls acted as a “pack” when they violently assaulted at least nine people inside a Perth McDonald’s, police said.

The girls, aged from 12 to 15, reportedly attacked other businesses, including a Baskin-Robbins, for almost an hour in Perth’s western suburbs yesterday.

Police received reports about 5pm a gang of young girls was terrorising people outside a shopping centre in Cockburn in Perth’s western suburbs..

The girls had reportedly been approaching people outside before they moved into a McDonald’s where they harassed people and tried to rob them and steal a till from the restaurant.

So far police have identified nine people who they say were assaulted by the girls. One McDonald’s worker suffered a broken nose during the incident.

Witnesses told of how they felt terrified as the girls attacked young Macca’s workers and others inside.

They then made their way into a nearby medical centre where people had taken shelter from the mob.

“They just rampaged in, pretty much, and the receptionist lady was obviously trying to move her out, and that's when the girls just started punching her in the face,” Caitlin Gahleitner, who witnessed the incident, told 9 News.

“It happens quite regularly, and security are limited as to what they can do. It’s happening a lot.”

Another local woman said her mum had been at the medical centre for a check-up and had called her daughter, according to Community News.

Over the phone she heard,“yelling and screaming and chaos in the background and my mum crying my name saying help”.

She said inside the medical centre a receptionist was “repeatedly punched”.

“What the hell is the world coming to,” she said.

“Their behaviour was extremely aggressive as they were walking down the streets towards other people,” Sergeant Dave Eaton said.

He said the girls had been confronting people in the street before they entered the McDonald’s.

“There was, if you don’t want to describe it as that, but a pack mentality,” Sgt Eaton said.

Seven girls have now been arrested in connection with the incident.