A crash that left three people dead near Nelson this morning was caused by a driver fleeing police.

Two cars collided on State Highway 6 near Clover Rd at about 5.40am, police said.

Police have confirmed they tried to stop a vehicle on nearby Gladstone Rd.

"The car failed to stop and fled towards State Highway 6, overtaking a truck and moving onto the wrong side of the road where it crashed into another vehicle that was travelling north," Superintendent Mike Johnson said.

"Tragically three people have died as a result, two of the deceased were from the fleeing vehicle and the third person was an innocent member of the public.

"An outcome like this is the last thing police want to see."

Johnson said the next of kin were still being notified of the crash.

"We now have three families who have lost members and our thoughts are with them during this difficult time."

Johnson said this kind of incident was "extremely testing" for police, who aimed to protect their community.

"They are fast-moving, unpredictable and high-pressure situations that require quick judgements."

The crash will be investigated and the Independent Police Conduct Authority has been notified.

The latest crash brings the weekend road toll to eight.

Meanwhile, three people are in hospital with injuries after a crash in Northland overnight.

A St John helicopter rushed to the scene in Ruakaka shortly before midnight and a crew treated the injured parties.

One person was critically injured in the crash, and two others had serious injuries.

One patient was airlifted to Auckland hospital and two others were flown to Whangarei Hospital.

A police spokeswoman said just one vehicle was involved in the crash, which happened on Peter Snell Rd.

The vehicle had driven off the road.