Four children believed to all be under the age of 12 have been killed after they were hit by a car while riding their bicycles in Sydney.

Emergency services have described scenes of "chaos" and "carnage" following the crash on Saturday evening.

The youngsters were struck by a 4x4 on a residential road near a golf club in Oatlands, in the Australian city's northwestern suburbs.

There are reports the victims, believed to be from the Maronite Christian community, were three siblings and a family friend.

A post on the Living Maronite Facebook page said: "Tonight before you sleep we ask that you remember in your prayers a young Maronite family from our Parish who has been devastatingly affected by a serious accident.


"We keep them all in our prayers."

A fifth child, who was originally thought to have a critical head injury, is now in a stable condition following the crash along Bettington Road at about 8pm local time.

Two girls aged 10 and 13 were also taken to hospital for treatment.

The 29-year-old driver of the Mitsubishi was arrested at the scene. Police say he tested positive for alcohol after a roadside breath test.

He has reportedly been taken to hospital for mandatory blood and urine tests. His passenger, a 24-year-old man, was being interviewed by police.

The children who died have not been formally identified.

A spokesman for New South Wales' ambulance service, Superintendent Andrew McAlpine, said: "When the first crews arrived on scene they were confronted with carnage."

"Very, very difficult scene with obviously a lot of chaos. It's incredibly hard for all the emergency services, notwithstanding the loss the families have sustained.

"It's very, very difficult for police, fire rescue, paramedics to be confronted with such chaos and such carnage."

He said the service had "a number of support systems we've put in place this evening and that'll be ongoing through the coming week" to ensure staff were being looked after.