Mexican police say they have discovered six charred bodies on a street in the northern city of Tijuana.
A police spokesperson said the victims had been shot, then burned, in violence blamed on drug gangs.
Police say the discovery of the bodies Monday brings the death toll to 14 for Tijuana since Saturday.
Police say drug violence is on the rise in Tijuana after two months of relative quiet in the city across the U.S. border from San Diego, California. Almost 300 people have died in drug gang wars in Tijuana this year.
Also Monday, police say gunmen killed the head of the state police in Culiacan, Sinaloa.
Elsewhere, authorities say a severed human head with a note from the killers in a plastic bag was discovered in Culiacan Monday.
police officials say a human head with a threatening note for Mexican
law enforcement was discovered Saturday in Oaxaca.
Drug-related violence has soared recently in Mexico. Authorities attribute much of it to rival drug gangs, fighting for control of lucrative drug-smuggling routes.
Mexican President Felipe Calderon has taken steps to control the violence. Since taking office in 2006, he has dedicated tens of thousands of soldiers and police officers to the fight against drug trafficking.
Some information for this report was provided by AFP, AP and Reuters.