A Mexican crime boss has been murdered on the operating table as he had plastic surgery to change his appearance and remove his fingerprints.

Gunmen burst into the clinic where Jesus "El Kalimba" Martin was undergoing the procedure on Monday afternoon and killed him along with three other people, Puebla state prosecutors said.

Martin was wanted for allegedly leading a fuel theft ring that illegally taps into pipelines to steal petrol and diesel.

The practice is a risky but lucrative business that has become Mexico's second-biggest organised crime problem after drug trafficking.

Prosecutors said in a statement: "He was trying to change his identity with a series of plastic surgery procedures to alter his face and remove his fingerprints so he could not be identified.”

"The medical personnel involved are also being investigated," he said.

A total of 12 people were killed in Puebla on Monday in what investigators say was a settling of scores between rival members of Martin's gang.

Five were murdered in the village of Tlaltenango on a farm where authorities found tubes, valves and pumps for illegal pipeline taps, as well as three stolen vehicles.

Three other victims appear to have been bystanders caught in the crossfire, investigators said.

Prosecutors said the hits appeared to have been ordered by another crime boss known as "El Irving" who had the same rank as Martin within the gang.

Puebla is the epicentre of the booming fuel theft racket, which state oil company Pemex has estimated cost it €2.03bn since 2010.