The bodies of 15 men, all but one of them headless, were found on a street outside a shopping center in Acapulco on Saturday as police reported 27 people slain in the Pacific resort in less than a day.
The decapitated victims, all of whom appeared to be in their 20s, were discovered in an area not frequented by tourists.
Handwritten signs left with the bodies were signed by "El Chapo's People" — a reference to the Sinaloa cartel, headed by drug lord Joaquin "El Chapo" Guzman — said Fernando Monreal Leyva, director of investigative police for Guerrero state, where Acapulco is located.
The narco-messages indicated the Sinaloa cartel killed them for trying to intrude on the gang's turf and extort residents. Authorities said there were at least three minors among the dead.
Mexico's drug cartels have increasingly taken to beheading their victims in a grisly show of force, but Saturday's discovery 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 discovered in the Guerrero state capital of Chilpancingo.
Acapulco has been the site of fierce battles between drug gangs, and this weekend got off to a bloody start with 27 people killed there from Friday evening to early Saturday, Leyva said.
The dead included two police officers cut down on a main bayside avenue in front of tourists and locals; six people who were shot dead and stuffed in a taxi, their hands and feet bound; and four others elsewhere in the city. Two police officers were wounded when armed men attacked a police post in the city's Emiliano Zapata district.
"We are coordinating with federal forces and local police to reinforce security in Acapulco and investigating to try to establish the motive and perpetrators of these incidents," Monreal said.
The wave of violence in one of Mexico's biggest resorts was condemned by the federal government.
"Reprehensible acts of violence such as these underscore the need to fight with determination against organized crime," a statement from the Interior Ministry said.
At least 30,196 people have died in drug-related violence since President Felipe Calderon launched an offensive against cartels in late 2006.
Also Saturday, authorities said a small-town mayor was found dead in northern Mexico.
Saul Vara Rivera, mayor of the municipality of Zaragoza, was reported missing by family members Wednesday, Coahuila state prosecutors said in a statement. His bullet-ridden body was discovered Friday in neighboring Nuevo Leon state.
There were no immediate arrests.
At least a dozen mayors were killed nationwide last year in acts of intimidation attributed to drug gangs.
By SERGIO FLORES, Associated Press
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