Five decapitated bodies were found Monday outside a school near the northern Mexican city of Durango, where soldiers have now unearthed 168 bodies in a month-long search of hidden graves.

Authorities found the five bodies lying naked, with their heads nearby, in the small town of Pueblo Nuevo, adjacent to Durango, said the state prosecutor's office in a statement, without giving further details.

Ten male bodies and one female body were meanwhile found buried underneath a building in Durango, the prosecutor's office said, adding that soldiers were continuing with excavations.

Authorities have not provided information on who may have been behind those killings, which appear to be linked to the massive spike in drug-related violence in the country over the past four years.

Last month, authorities recovered 183 bodies from 40 mass graves in the northeastern state of Tamaulipas on the US border, which has been gripped by drug violence in recent months.

Authorities have made no links between the two sets of discoveries.

The shocking numbers of buried bodies provoked more criticism of the government of President Felipe Calderon and its failure to stem the bloodshed, despite a clampdown on organized crime involving tens of thousands of troops.

More than 85,000 people took part in a silent protest in Mexico City's main square Sunday to protest the growing violence that has left some 37,000 people dead since 2006, according to media counts.

(AFP)