A group of bus passengers overpowered two would-be robbers, beating one to death and leaving the other badly injured, Mexican police said Thursday.

The incident took place before dawn on the highway linking the northern cities of Monterrey and Durango.

Before the bus reached Saltillo, according to the passengers, one of the assailants rose from his seat and walked toward the back of the vehicle, brandishing a large wrench, while his partner approached the driver with knife in hand and demanded the riders' belongings.

When the man with the wrench began to move toward the front of the bus, several passengers jumped him, grabbed the wrench and beat him to death with it.

"The accomplice, when he saw what happened, threatened the driver to stop and let him escape, but as they were in a uninhabited area, he said to keep going to the nearest town," a police source said.

He said the passengers seized on the opportunity to attack the accomplice, "leaving him gravely injured."

The driver reported the incident to federal police when the bus reached the Monterrey suburb of Santa Catarina.

The Red Cross took the injured robber to University Hospital in Monterrey and personnel from the medical examiner's office removed the body of the dead man.

The bus was ordered to the Santa Catarina police station, where the passengers are being questioned, a spokesman for the municipal government told Efe.

Highway robbery is surging in Mexico and the roads of the northern states of Tamaulipas and Nuevo Leon - which includes Monterrey - are among the most dangerous in the country. EFE