At least 20 people have been killed in what Mexican police say is a violent feud between rival drugs gangs across the country.
More than 600 people have been killed by drug gangs this year
Police said bodies were found in several of the country's states from the early hours of Monday.
Some of those killed were found with evidence of torture or were wrapped in plastic bags, while others had had messages pinned to their bodies.
The killings are being blamed on drugs cartels fighting for control.
The bodies of five victims, two of them women, were found in a car parked at the entrance of an exclusive neighbourhood in the resort city of Cancun, reports say.
In Guerrero state, at least eight people were executed in 48 hours, police director Erit Montufar told the Associated Press news agency.
The AFP news agency said one of the bodies had a note on it reading: "Welcome to all those who want to ally with us. Yours truly, your friends. Ha, ha, ha."
The Mexican government has cracked down on cartels
Other bodies bearing the hallmarks of execution-style killings were found in Tijuana, Veracruz, Sinaloa, Michoacan and in Mexico City, reports said.
Last year, more than 2,000 people died in drug cartel-related violence - some of the victims were tortured or beheaded.
So far, more than 600 have been killed this year.
In January, Mexico's new President Felipe Calderon sent more than 3,000 soldiers to the northern border city of Tijuana to help fight drug trafficking and gang violence. More than 300 people were killed there in 2006.
This came a month after he dispatched 7,000 troops to Michoacan state on the Pacific coast, where more than 500 people died last year.
In a separate development on Monday, the Mexican army arrested more than 100 policemen in the northern state of Nuevo León, accusing them of having links to organised crime and being involved in acts of violence.