The youngster was with a 29-year-old woman and and a five-year-old girl when the crash happened in Huyton, Liverpool, at about 9.50pm on Friday.

Merseyside Police said the driver of the vehicle, a dark-coloured Fiat Ducato van, fled the scene in Astley Road.

A 24-year-old local man was later arrested on suspicion of causing death by dangerous driving and is waiting to be interviewed by detectives.

The victim was walking along Astley Road when the van turned off Hillside Avenue and into her path.

The five-year-old girl was taken to Whiston Hospital suffering from facial injuries, while the woman with the children was uninjured but treated for shock. It is not known yet if they were all related.

A Merseyside Police spokeswoman said a post mortem would take place later to establish the cause of death and house-to-house inquiries were taking place.

She added: "The matter has also been referred to the Independent Police Complaints Commission. Prior to the road traffic collision on Astley Road a police patrol car driving along Derby Road, Prescot, had spotted a van, similar in description to the offending vehicle.

"The van, which was travelling in the opposite direction, was being driven in a manner which attracted the attention of the officers. The officers turned the police car round, but by the time they had reached the Brookbridge roundabout they had lost sight of the van. Some time later the road traffic collision in Astley Road was reported to police."

Anyone who witnessed the incident is asked to contact Merseyside Police on 0151 777 5730, or Crimestoppers on 0800 555 111.