A statement from Guerrero state prosecutors says 10 to 15 armed men attacked a group of civilians Wednesday night in the town of Zitlala, near the city of Chilapa.
Spokesman Randy Suastegui said yesterday that the dead suffered gunshot and stab wounds.
A message related to an organised crime group was said to have been left with one of the bodies, but its content was not made public.
The area sees regular clashes between drug gangs fighting over the cultivation of poppies, the key ingredient for making heroin, and over trafficking routes toward the United States.