VERACRUZ, Mexico — Callers to the radio program were voicing support for the Matazetas, the Zeta killers.

Better they fight among themselves. Let them kill each other. Anything to rid us of thugs who long ago took control of our city and are slaughtering our people.

It is a sign of the desperation and deep outrage over surging drug-war violence that a shadowy group of vigilante killers is not only tolerated but welcomed by many in Mexico's third-most-populous state.

Yet, it also comes with a disturbing question: Just who is behind the killings of Zetas? Another drug gang? Agents acting on behalf of the government or military? An ad hoc group whose presence is tolerated by authorities as well as the public?

Coastal Veracruz, the gateway to Mexico for centuries of immigrants from Europe and beyond, a laid-back, beach-front vacation spot for legions of Mexicans, has become the latest state to be thoroughly sucked into the deadly and devastating drug war.

On Sept. 20, nearly three dozen half-naked bodies were dumped in broad daylight on a busy highway underpass in a well-to-do tourist area of Veracruz, the state capital. Fourteen more turned up days later — during a convention of the nation's top state and federal prosecutors. Then, on Oct. 6, barely 48 hours after announcing a major security offensive, military and police found 36 bodies, and 10 more turned up the next day.

In videotaped presentations, a group of masked men with military bearing have claimed responsibility for the spate of killings, portraying it as a cleansing operation. Many bodies had a "Z" for Zeta written on the back with ink marker, a witness said.

The mystery group announced it was in Veracruz as "the armed branch of the people, and for the people."

"We are asking officials and authorities who support the Zetas to stop doing so and let the armed forces know that our only objective is to finish the Zetas," the spokesman for the group told the camera. "We are anonymous warriors, without faces, proudly Mexican."

For years with the Zetas tightly in charge, and the public terrified into submission, the state had stayed relatively calm. But traffickers associated with top drug lord Joaquin "El Chapo" Guzman are believed to have moved in from the north months ago, with an eye toward seizing territory from the Zetas, who had long controlled Veracruz's valuable routes for smuggling drugs, migrants and contraband.

The "Zeta killers" burst onto the scene shortly before President Felipe Calderón deployed fresh military forces into Veracruz this month.

The vigilante group's sudden rise and the surgical precision with which the killers systematically picked off nearly 100 people in 17 days have led to conjecture among some people that they may be operating with implicit or direct support of the government or military.

Some suggest the June kidnapping, torture and killing of three marine cadets in Veracruz might have propelled the marine corps to begin acting outside the law. Officials dismiss such speculation, and others wonder why a group aspiring to be a clandestine death squad would post videos on YouTube.

The Zetas themselves started as the private military arm of the Gulf cartel, hired gunmen recruited from army elite forces to fight and kill the cartel's enemies. They evolved into a full-fledged trafficking cartel after splitting violently from their former patrons.

Vigilante gangs purporting to be defending society and working with some level of official complicity have acted frequently in Mexico in recent years. La Familia in Michoacán, which surged in Calderón's southwestern home state in 2005, claimed it was protecting residents from the Zetas.

In Veracruz, doubts and questions run deep.

"We are left with a lot of disappointment and suspicion," said Miguel Angel Matiano, a union leader for judicial employees in Veracruz who is lobbying for protection for his members. "What interests, what ties ... do the politicians have? You can't take justice into your own hands, but if you don't trust the authorities, you will turn to the other group."

"You don't know who's who these days," added a local television broadcaster who did not want to be named for fear of his safety.

Whoever the "Zeta killers" are, Veracruz seethes with terror and panic. Streets in the port city, normally bustling with night life, begin to empty around dusk. Marines based in Veracruz patrol the neighborhoods, conducting house-to-house searches, moving in convoys, dressed in battle camouflage and black balaclavas. Parents rush to pull their children from school at the faintest rumored hint of an attack. Approximately 30 families from the business elite have fled the city, according to one knowledgeable resident.

"There has always been violence, but it was hidden better," said Father Luis Felipe Gallardo Martin del Campo, the bishop of Veracruz. "Now the lid has been blown off."

Even Calderón, in a startling admission, recently said that the state of Veracruz had been "left in the hands of the Zetas."

More than 40,000 people have been killed in the expanding drug war since December 2006, when it began, according to government intelligence figures.

The Veracruz government has sought to minimize the horror the state is living, or cast it as part of a broader national phenomenon for which local officials are not responsible.