Only two major cartels remain operating in Mexico, according to a top Mexican law-enforcement official, but an estimated hundreds of smaller splinter groups have developed into criminal cells that affect the lives of untold numbers of citizens.

Speaking at an international anti-drug trafficking conference on Tuesday in Colombia, Mexico's chief criminal investigator told the Mexican newsmagazine Proceso that the two main drug-trafficking groups in the country are now the Sinaloa Cartel and the relatively newer Jalisco New Generation Cartel.

Tomas Zeron, head of criminal investigations for Mexico's attorney general, also said authorities have identified only three cartel capos still heading these organizations: Ismael "El Mayo" Zambada and Fausto "El Chapo Isidro" Meza, for the Sinaloa Cartel; and Nemesio "El Mencho" Oseguera, a little-known figure who is believed to be in charge of the Jalisco New Generation Cartel.

"These are the cartels I have identified as working and functioning [in Mexico]," Zeron said in Cartagena on June 9, adding that "hundreds" of independent cells are also active.

The statements were the most frank assessment made in years by a high-ranking Mexican official about the criminal landscape of the country.

But Zeron's claims contradicted information released only a month ago by Mexico's attorney general's office, which told the newspaper El Universal in May that nine cartels are active threats in Mexico, and said at least 45 criminal cells operate throughout the country.

The US-backed campaign to dismantle the leadership structures of these groups have produced several high-profile arrests in the last year, such as the February capture of the Knights Templar boss Servando "La Tuta" Gomez, and the February 2014 capture of Joaquin "El Chapo" Guzman, former capo of the Sinaloa cartel.

Mexico's government has also captured or killed top leaders of the Zetas, Gulf, Beltran Leyva, Juarez, and Tijuana groups in recent years.

The Zetas 'have reached a point of near disintegration.'

A side-effect of taking out cartel bosses is a snowballing splintering of groups breaking off from once stable criminal organizations to stake claims of rackets such as extortion, kidnapping, and drug production and distribution, experts say.

Mexico's government blames the country's persistent violence on "internal power struggles" between competing cartel factions, dismissing the idea that innocent civilians are mostly caught in the crossfire. The rest "are cells that are seeking power in order to survive, and right now that's being reflected as homicides between themselves," Zeron said.

All that is left of the infamous Gulf Cartel, Zeron went on, is "the hit men, who once executed their enemies, but are now becoming leaders," and the Tijuana and Juarez cartels "have been taken over by Sinaloa."

As for the Zetas — known as one of the most innovative and technologically advanced in the country — they "have reached a point of near disintegration," Zeron said.

A burning vehicle blocks a road accessing the municipality of Paracuaro, Michoacan, January 10, 2014. (Photo by Ulises Ruiz Basurto/EPA)

More than 120,000 people have been killed in Mexico's drug war since former President Felipe Calderon sent Mexican soldiers to the state of Michoacan to combat entrenched trafficking groups there.

In the first three months of 2015, 8,845 violent murders were reported in Mexico, according to official figures, and more than 33,000 homicides were counted nationwide in 2014. In early January, Mexico's statistics institute said 67.9 percent of the population believe they are unsafe in their cities or communities.

The Mexican government, however, has not released official figures on homicides directly linked to organized crime in 2014. The only data available comes from media reports, researchers, and human rights observers. Some of these groups say organized-crime violence is diminishing.

"Between one third and half of all homicides in Mexico in 2014 were attributed to organized crime groups, which may signal a slight reduction in the proportion of such homicides," said a 2015 report on drug violence in Mexico from the University of San Diego.

Zeron called the Jalisco New Generation Cartel, considered one of the fastest growing and most powerful in Mexico, a "red flag." Since its formation just five years ago, the cartel has been terrorizing the western part of the country as it makes gains across Jalisco, Guanajuato, Michoacan, Colima states.

In late April, the New Generation cartel launched a series of violent coordinated attacks across Jalisco and four other states, in response to a government operation to capture "El Mencho," the cartel's leader. The Jalisco cartel downed a military helicopter on May 1. The group is also now reportedly entering Baja California and its border hub of Tijuana.

According to the 2015 report "Drug Violence in Mexico," drug-related homicides have decreased in conflict border states like Chihuahua, but continued to be a problem across the country, increasing in states like Veracruz, Michoacan, Sonora, and Guerrero. Kidnapping and extortion remain at high levels.

Increasing violence against news reporters has also been cited by observers such as the Committee to Protect Journalists, which ranked Mexico on the seventh spot internationally of its "Global Impunity Index." When journalists in Mexico are killed, the group noted, the murderers usually remain unpunished.