Twelve bodies were found on Thursday in the central Mexican state of Guanajuato, local authorities said, attributing the killings to disputes between organized crime groups.
Guanajuato, a thriving industrial center that is also home to popular tourist destinations, is currently Mexico's most violent state, according to official homicide statistics.
The 12 bodies were found within two hours in five locations in the city of Salamanca, according to the state prosecutor's office, which is investigating the crime.
The victims -- three women and nine men -- were found on roads, bridges and avenues, their bodies bearing gunshot wounds and signs of torture, while one was dismembered.
The state prosecutor's office also said the perpetrators left messages in which a cartel claimed responsibility.
The bodies were found less than 24 hours after gunmen attacked a residential center for people suffering from addictions in the same municipality, killing four.
"This month of October has started with very high crime rates here. That makes 16 people (murdered) so far," Salamanca Mayor Cesar Prieto told reporters.
But he said the violence affecting the city was "a temporary issue" that flares up "when one group decides to attack another".
In Guanajuato, two cartels, the Santa Rosa de Lima and the Jalisco New Generation, are currently at war.
Hit by spiraling violence linked to organized crime, Mexico has recorded more than 450,000 murders since December 2006, when a controversial military anti-drug operation was launched.
New President Claudia Sheinbaum announced that she will present her national security plan next Tuesday.
