A man is in a serious condition after being stabbed twice by a stranger at a Christchurch service station.

Police are appealing for information about the armed offender, and today released an image of a man they want to speak to about the incident.

The stabbing happened at the BP service station on the corner of Edgeware Rd and Cranford Street in the early hours of this morning.

Police said a man and woman entered the service station at 6.30am.

Shortly after two men also entered the station and walked to a seating area. 

Police are appealing for information about the armed offender, and today released an image of a man they want to speak to about the incident. Photo / NZ Police

"As the man and woman left the service station, one of the men in the seating area made an offensive gesture towards them," said a police spokesperson.

"The man and woman continued on their way, but the man returned shortly after with another associate.

"He was then approached by one of the men in the seating area, and stabbed twice with a small knife."

The victim was transported to hospital in a serious but stable condition.

"The offender, who was unknown to the victim, was initially wearing a black top and black pants but later put on a red t-shirt with ITALIA on the back," said the spokesperson.

"Police would like to hear from anyone who can help us identify the offender, or anyone who has information which could assist our enquiries."

Anyone who can help is asked to call 105.

Information can also be provided anonymously to Crimestoppers on 0800 555 111.

Police say the offender was initially wearing a black top and black pants but later put on a red T-shirt with Italia written on the back. Photo / NZ Police