At least four men have been found decapitated and 12 others murdered in suspected drug violence in the last 24 hours, Mexican officials said on Thursday.
Three decapitated bodies were found in Mexico state, which surrounds the capital, and a fourth was discovered in the southern Guerrero state, police and government sources said.
Two of the grisly findings, which come three days before Mexicans vote in legislative elections, were made near Teotihuacan, home to some of Mexico's most famous pre-Hispanic pyramids.
"Two decapitated males, whose identities are still unknown (were found) by the side of the road," an official from the attorney general's office told AFP on condition of anonymity.
Another decapitated body was found in Tecamac and a head was found in Naucalpan, both in Mexico State.
It is unclear whether the head belongs to any of the bodies discovered on Thursday.
Another decapitated head found in Guerrero was that of a 33-year-old man, and was found in a "black plastic bag," a government prosecutor said.
Decapitation is frequently used by Mexico's bloody drug cartels as a way of settling scores. The drug gangs are engaged in a brutal turf war for control of drug routes to the United States that has killed an estimated 7,700 people since the beginning of 2008.
Once epicenter of the violence has been the northern border city of Ciudad Juarez, a stone's throw from El Paso, Texas.
Around 1,650 people were killed in drug-related violence in Ciudad Juarez last year. At least eight more were killed on Wednesday night, authorities said.
The city of 1.3 million people is now home to 8,500 troops who have been deployed by the government of Felipe Calderon, who has bet his presidency on a muscular campaign to clamp down on the cartels.
That gamble will be put to the test on Sunday in mid-term elections, when voters will choose who will occupy 500 seats in the Chamber of Deputies and scores of governorships and mayoralties around the country.