A security chief brought in to quell increasing violence has been found shot dead along with his wife in a north western Mexican border state.

Security chief Ricardo Nino Villarreal and his wife were killed over the weekend in Tamaulipas state, but their car remained unnoticed for a day until passer-bys alerted local authorities who discovered the bodies.

Mr Villarreal, a former general, had been dropped into the area around Nuevo Laredo to deal with the escalation of gang violence. The Zetas drug cartel and Gulf cartel consider the area – mere miles from Texas, America – their turf.

It is believed that armed assailants ambushed the couple as they drove through a neighbouring state, avoiding toll roads, in their compact car.

According to AFP hundreds of bullet casings were discovered at the scene of the crime.

It is not the first time a high ranking member of Mexico’s security forces has been killed. In May Colonel Salvador Haro Munoz, Tamaulipas’ chief of intelligence, was shot dead along with his two bodyguards.

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The border state continues to see increasing violence. Over the last four years protesters – who marched through Cuidad Victoria yesterday – estimate nearly 750 people have been killed or disappeared in the last four years alone.

Roman Catholic Bishop Antonio Gonzalez Sanchez questioned whether any progress was being made, despite accords being signed to combat crime.