Four people are dead and two injured following four separate fatal crashes overnight.

In the latest, a person has died after a single-car crash on State Highway 1 in the Ruapehu District at 5.30am on Sunday.

Police say the incident, south of Waiouru and near Springs Hill, has briefly reduced the major highway to a single lane in the area.

Earlier, at 1.15am, a motorcyclist fleeing from police died after he came off his bike at Auckland's Royal Oak roundabout and hit a parked vehicle.
The Independent Police Conduct Authority has been asked to investigate that crash.

Just after midnight a man died in near Towai in Northland after the car he was in struck a tree off State Highway 1.

The driver was taken to Kawakawa Hospital.

At Omanaia, also in Northland, a man was killed after becoming trapped underwater when the car he was in crashed into a creek about 10pm on Saturday.

A second person in the car managed to escape the vehicle with only minor injuries, but the other man died at the scene, police said.