One person's in a serious condition after being pulled from a Campervan in Canterbury.

The crash occurred just after midday on Main North Road between Gressons Road and Macdonalds Lane.

It's understood three others have been injured. Earlier reporters indicated that three vehicles were involved. 

There has also been a four-car crash at Tiakitahuna, south-west of Palmerston North.

Two people are believed to be in a serious condition, and four others in a moderate condition.

Police ask that motorists avoid the area if possible. 

Up north, a backlog of traffic is clearing following a multi-vehicle accident on Auckland's Southern Motorway.

Police and the fire service attend the scene of the crash, which happened around 9.50am, just before the Great South Rd southbound offramp.

Fire and Emergency NZ northern shift manager Colin Underdown said it appeared four cars had been involved in the accident.

Two fire trucks had been sent from Papakura and Manurewa. However one truck had been stood down so it did not appear to be a serious crash, Underdown said.

A police spokesperson said the crash appeared to be a nose-to-tail.