Mexican authorities are investigating the possible emergence of a new drug gang that appeared to take credit for six killings through a message left with the bodies, officials said.
The six men were found inside a car in the southwestern city of Chilpancingo, Guerrero state police said in a statement.
Next to them lay a message reading: "This will happen to all rapists, extortionists and kidnappers. Attentively, the New Cartel of the Sierra."
Authorities are investigating the authenticity of the gang, said an official with the state prosecutors office, who spoke on condition of anonymity.
The official said authorities had no previous knowledge of such an organised crime group.
The car was reported stolen hours before the bodies were found, according to the police statement. The owner told police that armed men intercepted him on a road and forced him out of the car.
One body was found stuffed inside a black bag and the rest were tied up.
At least seven major drug trafficking cartels operate in Mexico, but there are many smaller gangs throughout the country, often affiliated with one of the bigger groups.
The cartels have increasingly splintered since President Felipe Calderon launched an intensified crackdown after taking office in late 2006, deploying thousands of troops and federal police across Mexico.
Mexican authorities blamed the infighting for a surge of gang violence that killed nearly 25,000 people in less than four years.
Most recently, a fight for control of the Beltran Leyva cartel increased violence in central and southwestern Mexico, including Guerrero state, which is home to the resort city of Acapulco.