Two armed men were fatally shot by a passenger on Friday while trying to carry out a robbery on an intercity bus, Mexican authorities said.

The violence erupted on a bus that left from the Mexico City suburbs bound for Tepeji del Rio, a town in the central state of Hidalgo.

As the two assailants were taking money and personal effects from the passengers, one traveler got out of his seat, shot the robbers and then fled the scene, witnesses said.

Federal police, who are responsible for law enforcement on Mexico's expressways, cordoned off the area where the incident took place, but have yet to make any arrests.

The fatal shootings came a day after bus passengers overpowered two would-be robbers, beating one to death and leaving the other badly injured. That incident took place before dawn Thursday on the highway linking the northern cities of Monterrey and Durango.

Highway robbery is surging in Mexico and the roads of the northern and central states are among the most dangerous in the country. EFE