|More than 30,000 people have been killed since 2006, when the government began a crackdown on gangs. [File: EPA]
Police found the bodies of 15 slain men, 14 of them decapitated, on a street outside a shopping centre in the Pacific coast resort of Acapulco.
Police in the southern state of Guerrero, where Acapulco is located, said on Saturday that handwritten signs were left with the bodies, a common calling card of Mexico's cartels.
Acapulco has seen bloody turf battles between drug gangs in recent years.
"On the sidewalk of the Plaza Senderos shopping centre were the decapitated bodies of 15 males, between 25 and 30 years of age," said the police report.
"The heads were found in one single place, with the exception of one that was half severed from the body and with an impact of a projectile from a firearm."
It was the largest single group of decapitation victims found in recent years. In 2008, a group of 12 decapitated bodies were piled outside the Yucatan state capital of Merida. The same year, nine headless men were found in the Guerrero state capital of Chilpancingo.
In keeping with a policy designed not to give the cartels publicity, state police did not release the text of the messages found with the bodies.
But Reforma newspaper reported that they referred to the Sinaloa cartel, headed by Joaquin "El Chapo" Guzman.
Reforma said they apparently indicated the victims were killed by the Sinaloa cartel for trying to intrude on the gang's turf and extort residents.
Bloody turf war
Several Mexican states have become the focal point of turf wars between drug cartels who seem to take pride in the mounting body count their battles leave behind, sometimes displaying bodies, other times posting Youtube videos of their kills.
Guerrero, the southwestern state where Acapulco is located, is a stronghold of the notoriously bloody La Familia drug cartel, which is waging a war with the equally dangerous Zetas and its ally the Pacifico Sur.
The Pacifico Sur cartel has been blamed for the September 30 kidnapping of 20 Mexican tourists who are believed to have been mistaken for La Familia rivals. The tourists' bodies were unearthed a month later in a mass grave near Acapulco.
In November, one Mexican hitman boasted to Al Jazeera that he had lost track of how many people he'd killed as he travelled from city to city, carrying out hits for his boss.
And in December, the Mexican army arrested a 14-year-old US citizen nicknamed "El Ponchis" (or, "The Cloak") who allegedly worked as an assassin for the South Pacific Cartel, in the state of Morelos.
More than 600 people have been killed in the past year in the northern state of Nuevo Leon, where traffickers set up roadblocks in October, terrorising the general public.
And the state of Chihuahua is home the the city of Ciudad Juarez, known as a the country's murder capital, where over 2,000 people were murdered in 2010.
Last year alone, a record 12,000 murders were blamed on the drug violence.