A homicide investigation was launched after the corpses of nine men were found in the city of Morelos in Zacatecas, the state prosecutor's office said.
It came a day after nine bodies were found on an avenue in the city of Fresnillo, also in Zacatecas state, reports BSS.
Messages addressed to a rival criminal group were found with those corpses, authorities said.
They were dumped near a market two days after gang members blocked roads and burned vehicles in response to the capture of 13 suspected criminals.
Fresnillo is the city considered by its residents to be the most dangerous in Mexico.
Around 450,000 people have been murdered across the country since 2006, when the government launched a controversial anti-drug offensive involving the military, according to official figures.