Emergency services were called to Warne Street in Wellington at about 4.30pm after a red Holden sedan reportedly struck five people.

NSW Ambulance paramedics treated an adult and four children at the scene, but two of the children, two boys aged six and seven died a short time later.

The 34-year-old woman was airlifted to Westmead Hospital in a critical condition. The 10-year-old boy sustained serious leg injuries and was airlifted to the Children's hospital at Westmead and is undergoing surgery. The nine-year-old boy sustained minor injuries and was taken to Orange Base Hospital.

The driver of the vehicle, a 25-year-old man, allegedly left the scene, however he was later arrested about 9pm near Elizabeth Street in Wellinton after a short foot pursuit.

He was taken to Dubbo Police Station where he will undergo mandatory drug testing at Dubbo Hospital.

Acting Commander of the Orana Mid-Western Police District, Inspector Natalie Antaw said at this stage police couldn't comment on what charges would be laid, however the 25-year-old was assisting police with inquiries.

Police said they believed the children had been at the local pool, just up the road from the scene of the accident.

"Obviously it's tragic circumstances for the entire community and our thoughts are completely with the family and friends of the little ones involved, and also the rest of the community of Wellington," Inspector Antaw said.

Police have urged anyone who has any information or dash-cam footage that may assist police with inquires should contact Wellington Police Station or Crime Stoppers.

Crash Investigation Unit and Forensic Services officers will examine the scene, and local police will investigate further into what caused the crash.

At this stage police believe no further arrests will be made.

EARLIER: Two children are dead and three people injured after a driver crashed into them before fleeing in the NSW Central West on Tuesday.

Police believe a car had struck five people at Warne Street in Wellington, south of Dubbo, about 4.30pm.

NSW Ambulance paramedics treated an adult and four children at the scene, but, two of the children later died.

The adult and two other children have been transferred to hospital - one in a serious condition.

The driver of the vehicle involved left the scene before to speaking to authorities, NSW Police said.

One report said at least two helicopters and as many as 10 ambulance crews rushed to the crash.

Orana Mid-Western Police District officers have established a crime scene, which will be examined by specialist police from the Crash Investigation Unit.

Police investigations into the matter are ongoing.

Inquiries are continuing and anyone who may have information is urged to contact Crime Stoppers on 1800 333 000.