A 4-year-old boy is dead after being hit by a teenager's car which spun out of control onto a footpath.

Police today identified him as Nayan Samuel Woods. He died after being hit by a car while walking in central Christchurch just after 5pm.

Nayan was walking with his 6-year-old brother Jacob and his mother when a car lost control in wet conditions on Linwood Avenue, police said.

The car slid from side to side on the road before climbing the footpath and hitting the children. One News described the driver as a boy racer doing drifts.

Jacob suffered multiple fractures and was in a stable condition at Christchurch Hospital. His mother suffered minor injuries.

Charges will be laid against the 17-year-old male driver, the sole occupant of the vehicle, once police finish their investigation, Detective Sergeant John Gallagher said.

Alcohol did not appear to be a factor.

"This has had a devastating effect upon both families, none more so than the family of Nayan," he said.

In a separate incident, a 10-year-old boy was also killed in a two-car collision on the Hibiscus Coast, north of Auckland.

In the Hibiscus Coast Highway accident, two cars collided head-on 2km north of Hatfields Beach about 5.45pm.

A 10-year-old boy died. Another child was seriously injured, as were two adults. Two other adults suffered moderate injuries.

In Christchurch, witnesses said the car driver tried to perform CPR on the child who died.

Lois Maddock and partner Chris Hack were in their home nearby and heard a loud bang.

Ms Maddock said her sons, 14 and 12, were across the road on a sports field and saw the crash and a person come out from underneath the car.

"They are a mess. They thought it was their little brother and sister."

Ms Maddock ran to the crash site to see if she could do anything. "When I got down there I saw one [child] lying on the ground and the driver doing CPR, but it wasn't working. The mother was leaning over the other one."

Paramedics arrived and rushed to treat the children.

Mr Hack said: "When [the mother] got in the ambulance with the child that was breathing and screaming, I don't think she realised the other one was dead."

Ms Maddock tried to usher young onlookers away from the crash scene so they could not see the carnage. "We live on this street. It could have been my babies."

Those hit were local residents, Mr Hack said, and he often saw them walking down the avenue.

Linwood Ave is a long stretch of road with multiple lanes, and residents said it was often used as a racetrack by boy racers. The road was wet yesterday after rain during the day.

Police had an area around the crash site cordoned off last night while they investigated.

The injured 6-year-old was in a serious but stable condition in hospital.

The Hibiscus Coast accident kept the road blocked until about 9pm.

Police are investigating which car crossed the centreline, and the Waitemata serious crash unit is working to determine whether speed or alcohol were factors.

Sergeant John Roberts of Orewa said paramedics worked on the "primary school-aged" child for some time, but were unable to save him.

Another child and an adult were airlifted in the Westpac rescue helicopter to the Starship and Auckland City Hospitals. Both had serious injuries.

A St John spokesman said paramedics took three other people by road - one seriously hurt and one with moderate injuries - to Auckland City Hospital, and another in a moderate condition to North Shore Hospital.

It is believed at least one of the cars was local to the Orewa district.

- with NZPA