Breaking: Two children die after being struck by car

Two children have died after being struck by a car in Cabramatta. (ABC News)

Two children under the age of five were sitting in a pram when they were struck by a car at an intersection in Cabramatta.

Both children died, while their mother was treated for minor injuries.

The 56-year-old driver of the vehicle has been arrested and will undergo mandatory testing, with inquiries ongoing.

Two children have died after being struck by a car while sitting in a pram in Sydney's south-west on Wednesday.

Emergency services worked on the children, both aged under five, at the scene at the intersection of Joseph and Gilbert Street in Cabramatta before they were taken to hospital in a critical condition.

A 33-year-old woman who police believe to be the children's mother was treated for minor injuries.

The driver of the vehicle, a 56-year-old man, was uninjured. He was arrested and taken to hospital for mandatory testing.

The driver of the car has been arrested and will undergo mandatory drug and alcohol testing. (ABC News)

NSW Police Superintendent Tim Calman commended the "phenomenal" members of the public who provided assistance at the scene.

"We've had a number of motorists that have actually stopped and collectively have moved the vehicle onto its side, tipped it over in order to get one of the children from underneath the vehicle," he said.

A crime scene has been established and investigations into the incident are continuing.

Cumberland Highway is closed southbound in Cabramatta between John Street and Cabramatta Road West.