Police in the Mexican state of Yucatan have found the bodies of 11 men, decapitated and piled on each other.
They were discovered in a rural area outside the city of Merida. Police have given few details.
Correspondents say Yucatan state has largely been spared the deadly drug-related gang violence that has appeared in many other parts of Mexico.
On Wednesday, police in Tijuana found three headless bodies in the latest incident of gang-related violence.
The victims were found with their hands tied, along with messages referring to drug-trafficking. Their heads, found nearby, appear to have been burnt.
Officials said the incident appeared to be a settling of scores by cartels.
Last week, Mexico's political and security leaders launched an emergency programme to try to combat the rising wave of violence.
There have already been more than 2,700 drug-related deaths this year.
Measures include sacking corrupt police officers, two new prisons for kidnappers and strategies to combat money-laundering and drug-trafficking.
The national security pact was signed by prosecutors and leaders from across the political and regional spectrum.
The country has overtaken Colombia and Iraq for the number of kidnappings.
Anti-kidnap marches are planned for 30 August, a sign of the growing public fury.