Officials said the series of clashes with suspected oil smugglers in the town of Palmar de Bravo, just outside Puebla, also left 11 soldiers wounded.

Six alleged oil thieves, among them a female suspect, were killed in the shooting, according to Diodoro Carrasco, a spokesman for the regional government authority.

Officials said drug smugglers are diversifying their operations, sometimes stealing from pipes belonging to the state oil concern Pemex in a lucrative sideline.

Puebla is one of the areas where oil thieves strike most often, according to officials, who said the gasoline siphoning costs Pemex some two billion dollars each year.