The nine men and two women were found in Boca del Rio in the violence-plagued state of Veracruz, state governor Miguel Angel Yunez told Oliva Radio station.
They were found on Tuesday night just as thousands of people in the port city of Veracruz celebrated the annual carnival festival.
An AFP photographer at the scene saw bloodied corpses, some of them naked and with their hands and feet bound.
Yunez said the killings were part of a "war" between drug gangs around the major port city of Veracruz.
The Zetas gang and their rivals Jalisco New Generation are fighting for control of crime rackets and drug-trafficking routes to the United States.
Officials said violence also broke out at the port on Tuesday, leaving dead two suspected criminals and a member of the navy.
Interior Minister Miguel Angel Osorio on Tuesday had just announced the deployment of military police to fight drug gangs in the state.
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