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An Auckland taxi driver is in a serious but stable condition in hospital after a vicious assault by a passenger, police say.

The 23-year-old male driver picked up a passenger from Auckland's Viaduct area about 11.30pm yesterday and drove him to Bertrand Road, Mt Wellington.

"The driver was then assaulted, receiving multiple stab wounds," Detective Senior Sergeant Greg Cramer, who heads the investigation into the incident, said.

The victim drove himself to a nearby service station where members of the public assisted him and called an ambulance.

He underwent emergency surgery at Auckland Hospital.

"The injuries are extremely serious and the victim is lucky to be alive. He is not out of the woods yet," said Mr Cramer.

The offender is described as a brown-skinned male, about 180cm tall, of solid to athletic build and wearing a grey or sandy coloured 'hoodie'.

Police would like to hear from anyone who may have seen him nearby the Sebel Hotel getting into a dark green Lexus, or in the vicinity of Bertrand Rd, Mt Wellington last night.

Anyone with information that might be of interest to the Police should contact the investigation team at the Glen Innes Police Station on 0508 OPGLADE.