efe-epaVeracruz, Mexico

Armed men burst into a private party at a restaurant in the southeastern Mexican city of Minatitlan and killed 13 people, authorities said.

The violence erupted around 9.00 pm Friday at La Potra, an eatery in the city's Obrera neighborhood, according to police.

Survivors said that the gunmen started shooting after party-goers resisted the assailants' attempt to kidnap one of the attendees.

Five women, seven men and a child lost their lives.

Contingents of soldiers, marines and Veracruz state police secured the scene and began a search for the attackers.

Minatitlan, a city of more than 350,000 people in the southern part of the Gulf coast state, is the site of a major oil refinery and kidnappings for ransom have become common over the last 10 years.

The targets are typically people in the oil industry, physicians, teachers and ranchers.

Military intelligence analysts attribute most of the violence in Veracruz to a turf battle among three criminal organizations: Los Zetas, Cartel Jalisco Nueva Generacion and the Gulf cartel.

Though the main business of all three groups is the drug trade, they also engage in migrant-trafficking, protection rackets and kidnapping on an industrial scale.

The state offers rich pickings for the gangs.

Veracruz is home to one of Mexico's two largest ports, much of the country's oil industry and a thriving agricultural sector.

The governor who took office last December, Cuitlahuac Garcia Jimenez, pledged to significantly reduce the levels of violence within two years.

Garcia belongs to the same party as President Andres Manuel Lopez Obrador and can likely count on help from the federal government in redeeming that pledge.

In recent years, the state government has officially acknowledged the disappearances of as many as 5,000 people and there has been a determined effort to find and excavate clandestine graves and identify the bodies buried in them, though much of the actual work continues to be done by NGOs.

More than 600 clandestine graves have been located during the last eight years and authorities have recovered 518 bodies, 560 skulls and 53,606 fragments corresponding to men, women and children.

The largest concentration of bodies - 298 - was discovered at a spot known as Colinas de Santa Fe near the port of Veracruz.