Eleven decapitated bodies have been found outside the city of Merida on the Yucatan peninsula, heightening fears that Mexico's recent descent into violence has reached even heavily protected tourist areas.

All the bodies showed signs of torture and were tattooed with star signs and the letter “Z”, suggesting that they had fallen victim to the country's growing drug war, which has left more than 2,700 dead so far this year.

Merida is a popular stop-off point for tourists on their way to visit the Mayan pyramids at Chichen Itza. On the other side of the Yucatan peninsula is Cancun, a Las Vegas-style holiday destination popular with US tourists; an hour or so farther south of Cancun is the resort town of Playa del Carmen, where many US hotel chains have built five-star properties.

Perhaps inspired by the insurgency in Iraq, Mexican drug gangs have started to use mass beheadings as a macabre public relations tool.

In an incident two years ago, several severed heads were rolled across the floor of a nightclub in the southern state of Michoacan. Earlier this week, four decapitated bodies were found in Tijuana, across the border from San Diego.

The aim, according to government officials, is to create “an atmosphere of terror”.

Jose Guzman, a Yucatan state prosecutor, said that the heads from the bodies found in Merida were still missing. “We believe that the executions were an isolated incident and not part of a strategy to destabilise the state,” he added.

Critics say this is wishful thinking. The resurgence of drug overlords in Mexico — along with endemic corruption in the police force and military - has led to a near-nationwide collapse in security. In May, the country's chief of police was murdered and, according to a recent study, Mexico now has more kidnappings than Iraq and Columbia.

So far, Mexico's most notorious drug overlord, Joaquín “Shorty” Guzmán, remains at large. According to popular legend, Mr Guzmán pays $2 million (£1 million) in cash wherever he stays to ensure protection, never uses a mobile phone twice, and once managed to conceal 7.3 tonnes of cocaine in cans of chilli peppers.

In another incident, he paid off a police commander with $1 million in cash and five Dodge Ram SUVs, in exchange for permission to land a cargo plane without interference.

Public outrage over Mexico's soaring crime levels reached a new intensity a fortnight ago after the killing of a boy aged 14 after his businessman father paid hundreds of thousands of dollars in ransom money.

It was later alleged that a corrupt police detective was part of the plot.

The only consolation for Mexicans has been that the drug war had left the tourist industry unaffected. No longer: the discovery of the 11 decapitated bodies on the Yucatan peninsula has already made headlines all over the world.

In addition to those bodies, another decapitated body was found 50 miles to the east of Merida, in a town called Buctzotz. Like the others, it showed signs of torture.

President Calderón responded to Mexico's rapidly deteriorating security situation last week by signing a national security pact, including a promise to purge corrupt police officers.

He said that “a cancer of criminality” had spread across the country, adding: “It's not about looking for who was guilty in the past. We're all responsible.”

Analysts say that this marked an important change of strategy. Since coming to power in 2006 after a contentious election, President Calderón has used the military to chase down drug overlords, a policy that has been criticised for being too one-dimensional. After all, the protection of drug traffickers by the police and military — to many, Joaquín “Shorty” Guzmán is a Robin Hood figure — has made successful prosecutions extremely difficult, if not impossible, even with financial support from the United States.

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